zika in america. the cdc warns of a surge in cases. the virus is now striking pregnant women here. and farry tale ending. a little girl's unicorn on the loose, and a police chase like we've never seen before. "nightly news" begins right now. >> announcer:s from "nbc nightly news" with lester holt. good evening. what a wild day it has been, one o the most dramatic and intense days of this presidential campaign so far. hours after mocking, ridiculing and challenging donald trump on the debate stage, a rejuvenated marco rubio struck again today and then donald trump struck back with a surprise announcement of new jersey governor chris christie. it was all part of a nasty back and forth war of words between trump and rubio on the trail just four days before super tuesday. nbc's katy tur starts off our coverage. katy, what a day. >> reporter: lester, bigger in texas, and this endorsement certainly came as a big surprise. less than a month after he dropped out and just four days to go until super tuesday, chris christie is getting behind donald trump and trying to lay waste to marco rubio. >> ladies and gentlemen, it is my honor and my privilete to introduce the next president of the united states, donald trump! >> reportett d?nald trump added a little jersey pride to his texas swagger in fort worth today. former presidential candidate chris christie officially endorsing the front-runner. >> and i really was happy with this one right here. so, chris, thank you. we love you, man. >> it's all make-believe. >> reporter: less than a month ago christie was trying to tear down trump. >> i never said i could shoot somebody in the middle of fifth avenue and never lose a voter. i never called mexicans and rapists and murderers, i never said ban all muslims from the united states. >> reporter: the two often called bullies eviscerate marco rubio. >>awast night i thought that the deal of the night was when i looked over to rubio, and i said, you remember, you're b choker and we don't want chokers in our administration. i said you're a choker and you're a liar. >> reporter: trump again mocking rubio's state of the union water bottle gaffe. >> let's talk about our lightweight senator from florida. he doesn't have the talent. he doesn't have the temperament. he can never make us great. >> reporter: the endorsement perfect timing for trump after a bad debate that left him on the defensive r his inhair tans, a trump university fraud suit and not releasing his tax returns. the irs has said that there's nothing precluding you in its rules from releasing your taxes -- your tax returns with an audit. >> until my audit is simple, very simple. you're not going to see anything. when you see it, you're going to see it. but i'm not going to camp kate things. >> reporter: christie, a cunning politician who many believe could have bridged gaps in washington, is pickinginthe s me bet. sources familiar with thinking tell nbc news. but rubio after standing up to trump at the debate isn't going to go down without a fight. katy tur, nbc news, fort worth, texas. >> reporter: this is gabe gutierrez covering marco rubio's campaign. today he was riding high until the billionaire dropped the bombshell. how stunning was the christie endorsement? >> stunning, look. chris is an articulate guy. donaldesrobably needs a lifeline after last night and he called in chris christie. i respect that. i have more than my fair share of endorsements. >> reporter: this morning in dallas rubio had ripped into the front-runner. >> what we are dealing with here, my friends, is a con artist. >> reporter: mocking a series of trump's misspelled tweets. >> and i only reached two conclusions. number one, that's how they spell those words at the wharton school of business where he went or, number two, just like trump tower he must have hired a foreign worker to do his own tweets. he called me mr. meltdown. last night during the debate during one of the breaks, two of the breaks. he went backstage, he was having a meltdown. first, he had this little makeup thing applying like makeup around miss mustache, had one of those sweat mustaches and then wanted a full length mirror, maybe to make sure his pants weren't wet, i don't know. >> reporter: rubio's all-out assault coming after last night's republican debate in hues top. he berated trump for his hiring practice. >> if he built the wall the way he built trump towers he'll be using illegal immigrants to do it. >> reporter: his inheritance. >> if he hadn't inherited $2 million -- >> reporter: and his repetition of campaign slogans and now he's repeating himself. >> i watched hwm repeat himself five times four weeks ago. >> sh i saw you repeat yourself five times five seconds to go. >> reporter: rubio faces a ste climb four days before super tuesday. po ills s w thecoenator behind trump in all 11 states. what's crucial is rubio's home state of florida on march 15th trailing by double digits. you're guaranteeing that you will win. >> well win. >> reporter: what happens if you don't? >> we'll win florida. >> reporter: as rubio campaigns throughout the south tomorrow, he's expected to release his own tax returns, and he's kag on the gop front-runner to do the same, but lester on a day when rubio woke up owning the news cycle he found himself trumped. >> all righe, gabe. regarding some of thosn allegatioin by rubio. coming up w bve got the inside story of how undocumented worked at the site of trump tower. affirmative action i want to bring in our political director, the moderator of "meet the press" chuck todd. chuck, our new poll asked registered vountersi'hich f the following would be their reaction to trump as the nominee. 51% said scared, 24% said angry, and when you lmok at numbers like that and you look at that back and forth we jfst saw a moment ago, what do yok make of it? >> i have to say, it feels like every time we think public discourse has deteriorated to a new low we reach a new low. it's really stunning today that we've seen between trump and rubio. it is unpresidential doesn't even begin to describe it, but, look the fact of the matter is you've got to give the trump campaign credit here. this christie endorsement, timing and symbolism are big with endorsements. a lot of times they are overrated but the timing of it was brilliant. you have to say that. it shows you that this is a very sophisticated campaign that trump had. had this in his big o tricks ready to go when he needed it and the symbolism. he's -- chris christie is a card-carrying member of the republican establishment. if you believe there's five stages of grief going on, lester, the fift staie is acceptance with republicans. ristie is a big acceptor. >> republicans sulking out the headlines but lest we forget democrat voters in the south carolina primary tomorrow. what do we look for there? >> well, it should be a big win for hillary clinton. if it's not, it shows you that there is life in danders' campaign. nders needs to improve with african-american voters, and if he does that, we'll know because he'll come of her, but if it's a double-digit big win for her is could be a foreshadowing of a long night for bernie sanders on super tuesday. >> chuck todd, thank you. shock and horror in another american city tonight, the scene of this country's latest mass shooting. this time four dead including the shooter and 14 wounded after that gunman went on a rampage at multiple scenes. most of the carnage inside his place of work. nbc's migueling a maggier has the developments into the investigation. >> reporter: a chilling video on the gunman's facebook page. police say cedric ford used an assault rifle to hunt and kill his victims. close to 5:00 p.m. thursday two shootings at two intersections, twcho people are wounded before ford speeds away. he then arrives at work excel industries. tectetes say ford opens fire on a co-wrrner in this parking lot and tlvn enters the building. >> all of a sudden pop, po , pop, pop, pop, pop, pop. >> reporter: ford sight. >> following people out the back, and i thought he was going to shoot me. >> reporter: 14 are wounded and 3 killed. 24 minutes of terror only coming to an end when a police officer storms the building taking five as he enters. >> the only reason he stopped shooting is because that officer stopped the shooter. >> reporter: cedric ford had a 20-year criminal history, a felon charged with burglary, grand theft and carrying a concealed weapon. in court documents his ex-girlfriend asking for a protective order saying he's an alcoholic, violent, depressed. it's my belief he's in desperate need of medical and psychological help. police served that restraining order to ford at excel shortly before the shooting. dennis briton jr. tht ought once thought about his three children as he was rushed to the hospital. >> i didn't want to leavi them. i wasn't ready to leave yes. i didn't want to die. >> reporter: tonight heartbreakoin this small community for sadowski 34 and loved rock music and joshua higbee, 31, a young father who lovedvehis little boy. >> he didn't deserve this. none of the people deserved this. >> reporter: tonight several people remain hospitalized including one in critical condition. police say ford was armed with an assault rifle and a handgun. nbc news has learned the weapons were bought by an ex-girlfriend, though not the same girlfriend who filed that restraining order. leverett, we are told 200 to 300 people were inside the lawn mower company behind me and had that police officer not engaged the suspect quickly, the death toll could have been so much higher. lester. >> miguel almaguer tonight, thank you. there is for troubling news about the zika virus which has been linked to birth defects. there are now more than 100 cases in this country, and now health officials have confirmed several pregnant women in the u.s. have contracted zika with more cases expected. nokes's rehema ellis the centers for disease control had been on the lookout for pregnant women returning to the united states from countries where zika has been linked to microcephaly. today the cdc confirmed 9 pregnant american women with zika and is investigating another mob ten. >> we described women who developed zika after traveling, got it from a place where zika is spreading and then are currently pregnant or delivered a child. >> reporter: two pregnancies ended in abortion. of the three babies born, one had the severe birth defect. nationwide the number of zika cases is growing. there are now 24 states and washington, d.c. with confirmed zika virus. at least 107 cases so far, all involving people who have traveled abroad and now doctors at seattle children's research institute in washington are sounding the alarm that the birth defect linked to zika could be even m e devastating than wioriginally feared. in brain scans cases doctors found a by's brain with zika was so severely damaged it was almost gone. >> suddenly seeing something this severe and this new in such numbers is unpress denchtd. i've never seen the like in my career. >> reporter: tonight health officials are warning there could be thousand of zika cases in puerto rico this summer, and the race is on to distribute mosquito protection kits there. raheema ellis, nbc news, new york. still ahead tonight, millions saw donald trump accused in last night's debate undocumented workers at the site of his trump tower. what really happened? 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(cghldred giggle) symbicort. u breathe better starting within 5 minutes. call or go online to learn more abteout a free trial offer. if you can't afford now to that controversy that has roared back into the headlines about donald trump and one of the most famous properties that bears his name, trump tower. trump, who vows to deport all undocumented immigrants, was accused in last night's debate of using undocumented labor himself at the site of trump tower. nbc news has investigated what went on there for months now, and tonight nbc news senior investigative correspondent isn'tiaia mcfadden reveals what we found. >> reporter: last night marco rubio let loose on donald trump. >> you lied about the polish workers. >> yeah, yeah, yeah. >> that was 38 years >> i guess there's a statute of limitations on lies. >> reporter: in the 1980s undocumented immigrants did do much of the initial work on the crown jewel of his empire in new york, trump tower,eshich raises the question is donald trump a hypocrite? is it accurate to say that trump tower, the construction of it, began on the backs of polish workers who are unpaid? >> oh, absolutely. it's c grstpu ied on theblood,ksweat o and tears of the polish brigade as they were known in the industry. >> reporter: back then attorney wendy sloan sued donald trump, his company and others claiming they failed to acknowledge at least 150 undocumented polish men working off the books. donald trump testified and was asked what rking off the books moin the construction industry meant. his respon ense, i really don't know. >> reporter: they had no protective equipment, no helmets, hard hats. >> reporter: in his 1990 testimony donald trump denied he knew illegal. did it ever come to your attention that any of those polish workers were illegal aliens? >> i really still don't know that. nobody has proven to me that they were illegal aliens. >> reporter: >> it seems he was saying in essence that everybody else in town knew what was going on on his own job site and he didn't. >> reporter: daniel sullivan, a labor relations consultant who had been convicted of tax evasion, testified that during the demolition trump himself knew he was using illegal workers on the site. >> there's no question in my min i mean, he shade it to me point plank. >> reporter: nbc spoke with sullivan in 1989. he has since died. >> donald's lying. flat out. he knew exactly what was happening. >> reporter: one of those workers says he was promised $5 an hour but wasn't paid for all of his work. must have been angry? >> very angry about that. >> reporter: he was one of only a few several undocumented workers testified at the time they were making only $4 an hour while the american union workers were making 12 to 14. they also said they were not paid for months of work, but at the time were too afraid to protest outside the building. >> they are looking for not legal people so that people are very afraid of all of that. >> reporter: mr. trump told us it was the ntractor's responsibility to pate demolition workers, not his, and a federal court agreed. still, he never reported the workers or tried to get them deported. mr. trump also told us he would have done nothing different. agmen, last night, defended himself. i'v hired tens of thousands of people er my lifetime. >> many from other plcountries instead of hiring americans. >> let me talk. i've hired tense of thousands of people. he brings up something from 30 years ago. it worked out very well. >> the law was totally rdifferent. it was a totally different world. >> reporter: in spite of what rubio claims what trump ultimately paid to settle the matter was sealed by the court. nonetheless, iouthe final ruling on yet another case involving the polish workers and trump tower, the u.s. court of appeals wrote at in the end time generalay reveals what a falsehood hopes to hide. but when it comes to mr. trump's appeal among voters consider this. mike, one of the polish workers who didn't get fully paid, told me he thought donald trump might be a very good president and was considering voting for him. lester. >> cynthia mcfadden tonight, thank you. we're back in a moment with that irs hack, far worse than we were first told. how you'll be able to te your body was made for better things than rheumatoid a thritis. before you and your rheumatologist move to a biologic, ask if xeljanz is right for you. xeljanz is a small pill for adults with moderate to severe ra for whom methotrexate xeljanz can reduce joint pain and swelling in as little as two weekl, and help stop further int daman.. xeljanz can lower your ability to fig yo infections, including tuberculosis. serious, sometimes fatal infections, lymphoma, and other cancers have happened. don't start xeljanz if you have an infection. tears in the stomach or intestines, low blood cell counts, and higher liver tests and cholesterol levels have happened. your doctor should perform blood tests before you start and while 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fighter of his own as a young man before moving into acting, appearing in six "rocky" films in all. he was 78 years old. the 88th academy awards are this sundaynd it'n one of the most competitive in recent history. many stre betting leonardo dicaprio will take home his first best actor oscar for "the ref advantage" mand brie larsonuis the best actress favelite for "room" and overshadowing is all is controversy. some like spike lee and will smith are boycotting the awards because of lack of color in the top acting cat guess naace. great unicorn escape and chase had many wonders what exactly were they seeing. ibs-d. yo geknow the symptoms when they start. abdominal pain. urgent diarrhea. now there's prescription xifaxan. xifaxan is a new ibs-d treatment that helps rmpieve yoe ur da rrhea and abdominal pain symptoms. and xifaxan works differently. it's a prescription antibiotic that acts mainly in the digestive tract. do not use xifaxan if you have a history of sensitivity to rifaximin, 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she belongs to 5 yelled tatum. >> reporter: juliette wears the horn to pose with professional pics with children and during the shoot this week she made a run >> she got afraid and runned away. >> reporter: and dashed through orchards and darted in and out of traffic. >> she turned out to be stealthier than we would have imagined. >> reporter: a situation reminiscent of last year's llama drama in arizona. juliet was eventually wrangled by a neighbor with a horse that lured the majestic pony out of hiding. >> the call came out that the 00 corn was in custody. as tbs tense as the situation was, taat was the comedic relief that was needed at the time and i laugh and i cried. >> reporter: while juliet escaped the wrath of the law, tatum was not so generous. >> she got in a time-out because she was being a bad pony. >> reporter: her unicorn horn is now gone replaced with two other horns, but at least everyone in this fairy tale lived happily everyt after. joe fryer, nbc news. >> and that will lgave us with a smile on our face on this friday night. i'm lester holt reporting from los angeles. for all of us at noc news, thank you for >>em> trump, rubio, and cruz's vicious, nasty, mud-slinging smackdown. >> presidential debate of an episode of "when animals attack"? now, on "extra." >> from king of the gop jungle -- >> thi guy's a choke artist and this guy's a liar. >> to trump skinned alive by a bloodthirsty cruz and rubio. >> no, no, no. >> can the donald roar again