‘Polite’, ‘Shy’ to ‘Troubled’, ‘Sick’: Portrait of Orlando Shooter Emerges

His ex-wife said he was clearly a "sick person" who finally "went crazy." His father said he was a "polite" young man whose actions can't be explained. A former co-worker said he was "filled with rage." A childhood friend only said he was "different."

A day after New York native Omar Mateen, 29, killed 49 people and injured 53 others before being gunned down at a gay nightclub in Orlando, Florida, a picture is beginning to emerge of a troubled man who may have been able to hide his hate even from those closest to him.

Sitora Yusufiy, the 27-year-old ex-wife of Mateen's, told ABC News Sunday that her former husband was short-tempered and abused her during their brief marriage in 2009.

"He would be perfectly normal and happy, joking, laughing one minute — the next minute his temper… his body would just [go] totally the opposite," Yusufiy said. "Anger, emotionally violent and that later evolved into abuse, to beating.

"After being abused and after trying to do that and see the good in him, I can honestly say this is a sick person. This was a sick person that was really confused and went crazy," she said.

Mateen's father, Seddique Mateen, said he didn't know anything about his son's alleged abuse of his ex-wife and had no explanation for why his "polite" boy would kill anyone.

"I couldn't believe that was my son," Seddique Mateen said. "He had a lot of love and care and I couldn't believe that this is what he was doing. If he was alive I would ask him one question, 'Why?'"

Seddique Mateen said his son was not an extremist and he had seen him Saturday afternoon, just hours before the shooting.

“It makes me upset, it makes me mad that I didn’t see anything unusual," he said.

Seddique Mateen said a few months ago his son had witnessed two gay men being affectionate in public in Miami and got upset, but the father said he didn't think much more of it.

Outside of his family, a former co-worker of Mateen's said it was obvious to him that Mateen was "had a lot of rage in him."

"When I say that he was unstable or unhinged, I mean this is a man who would lose his temper for no reason. He would kick walls, slap desks. I’ve seen him throw the chair across the room one time," said Daniel Gilroy, who used to work at a community security gate alongside Mateen. Mateen had been employed by the G4S security firm since 2007, the company said.

"I’m not surprised at what he did. I always knew he had something in him like that. And if I had to pick one person that would be capable of that, it would be him," Gilroy said.

Another acquaintance, childhood friend Sean Chagani, told ABC News Omar Mateen was clearly "different" but was shy and didn't show any hints of violence all those years ago.

"It's kind of hard to define. Was he violent? By no means was he a violent person. By no means did he express violent tendencies or any aggression in any way," Chagani said. "I guess everyone is a little bit different or quirky or unique. Omar was just different. I just don't know how to put it."

Overnight the terror group ISIS used another term to describe Mateen: "soldier" of their "Caliphate in America." Officials said Mateen called 911 in the midst of his attack to pledge allegiance to ISIS's leader, but terror analysts said that so far there's no evidence ISIS directed or had foreknowledge of the attack.

"This is likely to be somebody who is self-radicalized on the internet and decided on his own, what the target was and when to attack it," said former White House counter-terrorism advisor Richard Clarke, now an ABC News consultant.

Today the FBI continues its investigation, attempting to answer questions, including several about its own interactions with Mateen prior to Sunday's shooting. The FBI said Mateen had come to their attention in 2013 and 2014 for potential links to extremism. The FBI investigated, including conducting three interviews with Mateen, before determining he was not a threat in both cases.

After Mateen's divorce from Yusufiy in 2011, Mateen was remarried. At the time of the shooting, he had a young son with his second wife.