villanova parade. tonight, war of words. the democratic race takes its nastiest turn yet, as clinton and sanders spar over who's qualified to be president. manhunt for a campus killer. as a student is found dead. tonight, video of a person of interest revealed as fear sweeps the university of texas. cancer blood test a cutting-edge new way to target treatments for lung cancer. it's faster, less painful and a new hope in the fight against one of the deadliest forms. weight loss wonder. eat all your favorite foods and still lose those excess pounds. a technique once shunned, now doctors say it really works. life-saving surprise. a teacher, a student and a grandmother called to the principal's office. wait until you see the moment that brought everyone to tears.

"nightly news" begins right now. >> announcer: this is "nbc nightly news" with lester holt. good evening. move over, republican candidates, tonight it is the democrats grabbing the limelight with the nasty back-and-forth over a basic but awfully important question, who is qualified to be president. the heat has been building in the democratic race after bernie sanders' this week in wisconsin and hillary clinton defending her lead in her home state of new york where they elect two weeks from now. >> reporter: tonight a turning point in the campaign. democrats no longer taking the high road. >> if you want to question my qualifications, let me suggest this. that maybe the american people might wonder about your qualifications, madam secretary, when you voted for the war in iraq. >> reporter: bernie sanders accusing hillary clinton of starting the fight.

over who's not qualified to be president. a war of words sparked by this exchange on morning joe wednesday. >> do you think he is qualified? >> i think what he has been saying about the core issue in his whole campaign p doesn't seem to be rooted in an understanding of either the law, or the practical ways you get something done. >> reporter: after a photo opportunity on the subway and a little trouble with a fare card, clinton responding today in a bronx diner with matt lauer. >> he came right out and said he doesn't think you're qualified to be president. >> well, that will be up to the voters of new york and the other states that will be passing judgment in the weeks ahead. i think it's kind of a silly statement. but he's free to say whatever he chooses. >> reporter: for months, democrats have been bragging that they don't fight like republicans. >> the american people are sick and tired of hearing about your damn e-mails. >> reporter:

encouraged by his success, sanders is shifting gears as he wins states, despite the daunting delegate map. will democrats be able to unite? one out of every four sanders supporter say they won't back clinton. this warning from clinton sanders' campaign manager. >> it's imperative that enough democrats speak up and say stop this. neither side is entirely blameless here. again, i call on both of them to remember why they ran. >> tonight the white house saying the president believes clinton is qualified. and party leaders are warning both campaigns that having the two democrats accusing each other of being qualified is giving in to attack ads in the fall. >> tomorrow morning, on "today," plus a live town hall with

bernie sanders out on rockefeller plaza. meantime, it is no less nasty on the republican side. trump and cruz waging their war for new york, and donald trump is now adding new top staffers and laying out a new strategy after a tough defeat in wisconsin. nbc's peter alexander has those details. >> reporter: donald trump today holed up in his manhattan high-rise, facing fierce criticism, trump's campaign will announce new hires. >> we need more brains and we need more muscle. mr. trump is the force. >> reporter: after a weak showing in wisconsin, trump scrapping a planned california trip friday and skipping colorado to focus on fortifying his lead in his home state. >> it's great to be home. this is home. it's great to be home. >> reporter: why? trump now needs 59% of the remaining delegates to clinch the nomination. sweep new york, and that number drops to 53%. today touting the support of former new york city mayor rudy

giuliani. and reaching voters in neighboring states, all with upcoming primaries. his challenger zeroing in on individual congressional districts, looking to peel away delegates. ted cruz with orthodox jews in brooklyn. john kasich getting a taste of an italian neighborhood in the bronx. >> we love new york values. it's a great place. >> reporter: about those values, trump again attacked cruz. >> when he started lecturing me on new york values, like we're no good. like we're no good. >> reporter: cruz casting trump like hillary clinton as a liberal. >> they want to see a general election between two new york liberals who agree on washington being the center of the universe. >> reporter: a new poll shows 7 in 10 americans have a negative view of the front-runner, but he's hugely popular among new york republicans. >> now i'm a republican just so i can vote for trump. >> reporter: the billionaire banking on an embrace from the empire state.

peter alexander, nbc news, new york. . tonight fear is sweeping across one of the biggest colleges in america. a murder mystery on the campus of the university of texas at austin where a young dance student was found dead in a creek. now authorities are asking for help identifying a man caught on camera being described as a person of interest. nbc's gabe gutierrez is there. >> reporter: tonight an urgent manhunt for this freshman's killer. she was just 18 years old, a dance major at the university of texas at austin. but now police confirming her body was found in a campus creek tuesday. >> as a parent, this is my worst nightmare. >> reporter: friends reported wiser missing on monday. police say she was last seen leaving a campus building the night before around 9:30. now authorities are looking for the man in this surveillance video, seen walking with a woman's bicycle at about 10:00 p.m., and again after 11:00 sunday night.

>> we need the community's assistance in this matter of identifying this person. >> reporter: wiser's death now prompting ramped-up safety measures on a campus of more than 50,000 students. >> it made me kind of check myself, to make sure that i'm being as safe as possible. >> lately, i don't like to walk home alone at night anymore. >> reporter: it's the first homicide investigation on the main campus here since 1966. when student gun mn shooting from the tower killed 14 people. the university already at the center of the debate over campus security with a new texas law allowing concealed guns on campus set to take effect later this year. but ut is remembering an oregon native trained in ballet and said she loved to dance because it challenged her. the school's president reading a statement from her family. >> if her death can somehow make it safer for a young woman to walk home, it will all prevent another assault or murder.

at least we can find some meaning behind an otherwise senseless and tragic death. >> reporter: at this hour, memorial services under way here on campus. $15,000 reward is being offered for any information leading to an arrest. lester, tonight more security, more light-night shuttles for students and dozens more officers on patrol. >> gabe gutierrez, thank you. a new look at one of the most wanted men in the world. belgian authorities released new video of the terror suspect at the scene of a deadly airport attack in brussels more than two weeks ago. it shows him escaping the airport. and as our bill neely reports, investigators are desperate for new leads to catch him. >> reporter: until now, we've seen him just once, with two suicide bombers, before committing mass murder at the airport. new images show the man in the hat, what he did next. minutes after the bombing and the

suspect walks past a nearby sheraton hotel. new video shows him walking calmly, then jogging. he speaks to no one. he has left behind carnage. 16 dead, with more to come. 8:50, he's thrown his jacket away. the next bomb in the metro will explode in minutes. the police video tracks him for six miles. at 9:42, he's still strolling. 16 people have just been killed in the metro. he appears again on a cell phone before his trail runs cold at 9:50. by then, he had walked to within a mile of the carnage of the metro. no one knows why. investigators want hip, even from tourists. >> we especially appeal to people who might have seen or taken a photograph of the sus speblts. >> reporter: two images of him talking worry analysts. >> we see his arm is crooked up. he's clearly communicating with others.

the big concern must be, are these individuals out there plotting another attack. >> reporter: today's appeal suggests police have run out of leads. they can't identify him. they can't find his discarded coat. and they can't find him. bill neely, nbc news. back in this country, millions are under extreme weather warnings from dangerous winds fanning wildfires to historic heat and cold. in the south, many woke up to reports of tornadoes. while in the plains, crews are still fighting massive wildfires. nbc news national correspondent miguel almaguer takes us to the front lines of the battle. >> reporter: 200 firefighters near the town of freedom, oklahoma, are making slow progress against the largest wildfire that has scorched 80 square miles. but tonight the wind is as dangerous as the flames. nine separate wildfires fanned by powerful gusts, fueled by the drought. >> it's been very rapid, fast-moving fire behavior.

>> reporter: the fire devastating for ranchers, now victims counting their losses. >> we lost about 60 cows and 59 calves. some of the other cattle we don't know about yet. >> reporter: much of the plains is a tinderbox. 8 million are under a red flag warning, extreme fire conditions, with 35-mile-an-hour dry and hot winds. in the southeast, wind of a different kind. reported tornadoes in florida, georgia and alabama, homes shredded when violent weather hit overnight. several injured while they were asleep. >> banged up. it could have been a lot worse. >> reporter: in michigan, a bitter blast. some temperatures across the region, 25 degrees below average. arctic cold from canada, seesawing into the weekend. saturday will be frigid. in the pacific northwest, the polar opposite. record highs, 25 degrees above average. a spring of extremes

bringing it all, heat, ice and flames. miguel almaguer, nbc news, freedom, oklahoma. we want to tell you now about promising news about the new frontier in fighting cancer. it's a pioneering blood tests that allows doctors to particularly target treatment for the cancer that kills more americans than other. as ann thompson explains it's far quicker and easier than a traditional biopsy and it doesn't require surgery. >> reporter: what if a simple blood test could replace invasive biopsy to quickly find the best cancer therapy. a new study says that's what a liquid biopsy can do, to fight the most common type of lung cancer. and soon boston's cancer institute will offer it to all patients with non-small cell lung cancer. when one drug stops working, jeannie larson couldn't have a traditional biopsy to what to do next. >> i didn't want to

have another collapsed lung, like the time before. so i was very, very hesitant to do that. >> reporter: instead, this mother of two had a liquid biopsy to combat this nonsmoker's lung cancer that spread. here's how it works. cancer tumors shed dna into the blood. by analyzing the mutations, doctors can tell what new targeted therapies could be more effective and monitor their progress. the advantages, liquid biopsies are less painful, more accurate in detecting mutations, and most important, they are fast. results in three days as opposed to up to five weeks for traditional biopsies. >> we can get the result in a couple of days instead. it can have a really important meaning for those patients when they're sick with lung cancer. >> reporter: oxnard stresses the liquid biopsy cannot initially diagnose cancer and the hope is that some day it could be used in treating other cancers. now on a more effective treatment, jeannie larson is

planning ahead thanks to a simple blood test helping doctors and patients stave off one of the deadliest cancers. ann thompson, nbc news, new york. still ahead tonight, dramatic weight loss. growing evidence that a type of diet once rejected by experts really works. how this woman dropped over 100 pounds while still eating pizza and doughnuts. also, a wild car chase caught on camera. the suspect doing doughnuts in a the suspect doing doughnuts in a ♪jake reese, "day to feel alive"♪ ♪jake reese, "day to feel alive"♪ ♪jake reese, "day to feel alive"♪ or if you're young or old.e if you run everyday,

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in a world of weight loss, it goes by a variety of names. the every other day, 5-2, or the alternate day diet. by any other name, it's fasting, a dieting technique once shunned. now the medical community is saying it can work. there could be benefits beyond losing weight. here's nbc's janet shamlian. >> reporter: it allowed jennifer stewart to eat all her favorite foods. >> i love doughnuts. >> reporter: there was also cookies and pie. pizza and ice cream. >> when the weight started coming off, were you kind of surprised? >> yes, i was. i thought it was too good to be true. >> reporter: 18 months later the scale proved otherwise. starting at almost 300 pounds, she lost 110. and had a closet full of clothes like this. when you look at it now, what do you think? >> it's unbelievable. >> reporter: jennifer was intermittent fasting. once criticized by the medical community, now

gaining scientific endorsement. here's how it works, one day jennifer would eat only 500 cal lis, the next more than twice that amount, 2,200 calories. a plate that looks like this. nutritionists say the diet works because overall calories are reduced, and the high calorie days don't become outright binges. >> people are almost unable to binge on that day. they tend to only eat about 10% more than they would usually eat. we see that in about 600 or 700 people now. >> reporter: research shows fasting might also slow the aging process, and reduce the risk of cancer and diabetes. now on a maintenance plan with slightly higher calories, jennifer's lost another 20 pounds and gained her confidence. >> it shocks my family because they had no idea that i would ever lose weight. i had no idea either. >> reporter: a weight loss regimen showing results. when feast is combined with famine. janet shamlian, nbc

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here in southern california this afternoon, we watched wall-to-wall coverage of one of the wildest police chases in some time, on and off highways, through city streets, viewers captivated by a pair of burglary suspects on the run. nbc's gadi schwartz has the wild scene. >> reporter: a very wet and very wild high-speed chase in los angeles. this afternoon, we watched a dangerous police chase turn into an all-out joyride. it was raining, but the burglary suspects dropped the top on this mustang convertible and then started doing doughnuts on hollywood boulevard. along the famous hollywood walk of fame, pedestrians ran to avoid being hit. then on the freeway a tmz tour bus tries to box them in, but they slip away.

the mustang losing a tire. the chase finally slowing down in a south los angeles neighborhood and coming to a stop. the suspects appearing to wait for police while shaking hands and high-fiving with the crowd gathered on the street, snapping selfies before they are arrested. an apparent end to a very hot pursuit on the streets of los angeles. gadi schwartz, nbc news, los angeles. >> bizarre times. after seven months, we now know what to call one of the rare giant panda cubs. her name picked in a public contest means warm and friendly. she was born in august at malaysia's national zoo to parents on loan from china. china also loaned a pair of pandas to south korea where they got their close-up today ahead of a public debut. when we come back, a perfect match. one teacher's selfless gift to save a first-grader's life.

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livers. but one teacher in wisconsin gives new meaning to going above and beyond. nbc's kristen dahlgren tells us about her life-saving sacrifice for a student. >> reporter: the first thing you notice about natasha fuller is that impish smile. not how sick she is. after a lifetime battling kidney disease. >> she said, i just want to be like my friends. i just want to play like my friends. >> reporter: for the past few years the first grader has been living with her grandmother in wisconsin to be close to the hospital, hoping for a kidney transplant. but there was never a match. then one day her grandma was called to the principal's office. >> i thought she was naughty. i thought she got in trouble. >> reporter: and a woman she never met before handed her a present. a card saying she was a perfect match. third grade teacher jody schmidt is donating her kidney to

the little girl who always stopped to say hi as she walked by. >> you'll give me a hug? >> yeah. >> she's not even in your class. >> it's hard to explain. i just know it's the right thing to do. >> reporter: she called her husband. >> i said, i think i'm going to give a student a kidney. he said, okay. >> reporter: mrs. schmidt has three kids of her own. her family worries. but sometimes so does natasha. >> i'm scared, too. >> we'll be scared together. but we'll be okay. >> yeah. >> we can do all the things you want to do. >> like jump, tackle? >> reporter: it's a day that could come very soon. surgery is scheduled for later this month. >> i just keep thinking of the time that i get to see her after, when everything is done, and she's healthy. that's what i keep picture in my mind. >> reporter: kristen

dahlgren, nbc news, oakfield, wisconsin. >> wow. a story that makes you want to give the favorite teacher in your life a big hug tonight. that will do it for us on this thursday night. i'm lester holt. for all of us at nbc news, thank you for watching, and good knight. katie mcginty knowshool, get the routine. by. her dad was a philly cop. mom worked in a restaurant. then, hard work opened doors. now it's not quite enough. but mcginty's working to change that, helping create thousands of new jobs. she'll always stand up for manufacturing, higher wages, and equal pay for women so opportunity never gets out of reach.

katie mcginty for senate. women voters responsible for the content of this advertising. this is the 2016 democratic debate for pennsylvania attorney general. a race where money and geography matter. >> i have been an underdog any whole life. >> does experience