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" good evening. what a wild day it has been, one of the most dramatic and intense 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, they say everything is bigger in texas, and this endorsement certainly came as a big surprise. less than a month 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 privilege to introduce the next president of the united states, donald trump! >> reporter: donald 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 teaming up to eviscerate marco rubio. >> last night i thought that the deal of the night was when rubio, and i said, you remember, you're a choker and we don't administration. i said you're a choker >> reporter: trump again mocking rubio's state of the union water bottle gaffe. >> let's talk about our lightweight he doesn't have the talent. temperament. he can never make us >> reporter: the endorsement perfect timing for trump after a bad debate that left him on the defensive for 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 picking the sure bet. sources familiar with the governor's thinking tell nbc news. but rubio after at the debate isn't going to go down without a fight. ty 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. donald probably 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. let me tell you something. last night during the debate during one of the breaks, two of the breaks. he went backstage, he 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 repeating himself. >> i watched him repeat himself five times four weeks ago. yourself five times five seconds to go. >> reporter: rubio faces a steep climb four days before super tuesday. polls show the senator behind trump in all 11 states. what's crucial is rubio's home state of florida on march 15th where one poll has him trailing by double digits. you're guaranteeing that you will win. >> well win. 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 right, gabe. regarding some of those allegations by rubio. coming up we've 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 voters which of the following would be their reaction to trump as the nominee. 51% said scared, 24% said angry, and when you look at numbers like that and you look at that back and forth we just saw a moment ago, what do you 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 the back and forth today that we've seen between trump and rubio. it is unpresidential 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 brilliant. you have to say that. it shows you that this is a very sophisticated campaign that trump had. had this in his big of 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 fifth stage is acceptance with republicans. christie is a big acceptor. >> republicans sulking out the headlines but lest we forget democrat voters in the south carolina primary tomorrow. there? >> well, it should be clinton. if it's not, it shows you that there is life in sanders' campaign. sanders needs to african-american voters, and if he does that, we'll know because he'll come within single digits of her, but if it's a double-digit big win for her is could be a foreshadowing of a tuesday. >> chuck todd, thank shock and horror in another american city tonight, the scene of this country's latest mass 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 >> reporter: a chilling video on the 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, two people are wounded before ford speeds away. he then arrives at work excel industries. detectives say ford opens fire on a co-worker in this parking lot and then enters the building. >> all of a sudden pop, pop, pop, pop, pop, pop, pop. >> reporter: ford fires on everyone in >> following people out the back, and i thought he was going >> reporter: 14 are 24 minutes of terror only coming to an end when a police officer storms the building 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. thought once thought about his three children as he was rushed to the hospital. >> i didn't want to leave them. i wasn't ready to leave yes. i didn't want to die. >> reporter: tonight heartbreak in this small community for the dead. renee benjamin was 30, brian sadowski 34 and loved rock music and joshua higbee, 31, a his 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 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 country, and now health officials have confirmed several pregnant women in the u.s. have contracted expected. nokes's rehema ellis >> reporter: for weeks the centers for disease control had been on the lookout for pregnant women united states from 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 more devastating than originally feared. in brain scans comparing microcephaly cases doctors found a baby's brain with zika was so severely >> 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? tonight the results of an nbc news investigation into that. also, you're not just seeing things. that's a unicorn, sort of. and she led police on a wild chase that's no i built my business with passion. but i keep it growing by making every dollar count. that's why i have the spark i earn unlimited 2% cash back on everything i buy for my studio. and that unlimited 2% cash back from spark means thousands into my business... that's huge for my bottom line. what's in your wallet? go, go, go, go, go, go... touchdown! choir and harp music. this place, it's the best-kept secret in football since... hey, how did he get in here?! and with toe nail fungus! fight it! with jublia. r jublia is a prescription medicine used to treat toenail fungus. r use jublia as instructed by your doctor. now that's prime time. r most common side effects include ingrown toenail, application site redness, r r itching, swelling, burning or stinging, blisters, and pain. you ready to fight it? ask your doctor if jublia is right for you. y'know, i look great in purple. look, the wolf was huffing and puffing. like you do sometimes, grandpa? 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(children giggle) symbicort. breathe better starting within 5 minutes. call or go online to learn more about 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 ago. >> i guess there's a statute of limitations on lies. >> reporter: in the 1980s undocumented immigrants did do much the crown jewel of his empire in new york, trump tower, which raises the question is hypocrite? is it accurate to say that trump tower, the construction of it, began on the backs of unpaid? >> oh, absolutely. it's constructed on the blood, sweat 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 working off the books in the construction industry meant. his response, 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 the workers were illegal. did it ever come to your attention that any of those polish workers were illegal 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 mind. 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 polish workers with a green card. several undocumented workers testified at the time they were 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 contractor'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. again, last night, defended himself. >> i've hired tens of thousands of people over my lifetime. >> many from other countries 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. >> you paid $ -- >> the law was totally different. it was a totally different world. >> reporter: in spite of what rubio claims what trump ultimately matter was sealed by the court. nonetheless, in the final ruling on yet another case involving the polish workers and trump tower, the u.s. court of appeals wrote that in the end time generally 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 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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 sunday an it's one of the most competitive in recent history. many are betting leonardo dicaprio will take home his first best actor oscar for "the ref advantage" and brie larson is the best actress favorite 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 grace. coming up, the great unicorn escape and chase had many wonders what exactly ibs-d. when they start. abdominal pain. now there's prescription xifaxan. xifaxan is a new that helps relieve your diarrhea and abdominal pain symptoms. and xifaxan works differently. that acts mainly in the digestive tract. do not use xifaxan if you have a history of sensitivity to rifaximin, rifamycin antibiotic agents, or any components of xifaxan. tell your doctor right away if your diarrhea 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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 for the rainbow. >> she got afraid and runned away. >> reporter: and dashed through orchards and darted in and out of traffic. 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 pony out of hiding. >> the call came out in custody. situation was, that was the comedic relief that was needed at the 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 every after. joe fryer, nbc news. >> and that will leave us with a smile on our face on this friday night. i'm lester holt reporting from los angeles. for all of us at nbc news, thank you for what went wrong? was the nanny involved, or not? i'm billy bush with jennifer garner's first powerful words on her split with ben. >> no, i don't think it's healthy. >> putting a girl my size on the cover. i mean it's glamorizing them and your should be -- >> is the former si cover model out of line or making a good point? cheryl tiegs gets at least one