Father of Orlando Shooting Suspect: 'I Don't Think He Was Radicalized' Seddique Mateen said he saw his son Saturday and didn't notice anything amiss.

 -- The father of Omar Mateen, identified by officials as the shooter who killed at least 50 people at an Orlando gay nightclub early Sunday morning, said if he could ask his son one question, it would be: “Why?”

In an interview with ABC News at his home in Fort Pierce, Florida, Seddique Mateen said he was shocked and saddened to learn that his only son was the man authorities say is behind the carnage at Pulse nightclub.

“I didn’t see anything irregular with him. I saw him yesterday [Saturday] afternoon,” Seddique Mateen said. “It makes me upset, it makes me mad that I didn’t see anything unusual.”

Seddique Mateen and his wife were born in Afghanistan, and moved to the United States before having children. His son was born in New York and grew up in St. Lucie County, Florida. Seddique Mateen told ABC News his son was a family man and a devout Muslim who never showed any signs of extremism, violence or hatred.

“I don’t think he was radicalized,” Seddique Mateen said. “That’s what my gut feeling tells me.”

In an interview with ABC News, Omar Mateen’s ex-wife said he was religious but showed no indications of radicalism. Sitora Yusufiy said she was shocked by her former husband's attack.

As a husband, however, she said Omar Mateen was abusive and mentally unstable. When he was angry, he would sometimes rant about homosexuals, Yusufiy said.

“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, 27, told ABC News. “Anger, emotionally violent and that later evolved into abuse, to beating.

In the four months that they were married, Yusufiy said he cut her off from her family and regularly beat her. She said her family "rescued" her from the abusive marriage while visiting.

“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.

When she left Omar Mateen in 2009, Yusufiy assumed the “horrible mistake” she had made was long behind her. He had tried to contact her through Facebook a year ago, she said, but she blocked him. Then she turned on the news today.

“I thought I had closed the chapter on this horrible mistake that I had gotten myself into and forgot all about it and we’re free from it. But this is the most shocking, heartbreaking experience,” she said.

Seddique Mateen said this is the first he’s heard about his son’s abusive behavior toward Yusify. Omar Mateen later remarried and had a 3-year-old son with his new wife. Seddique Mateen said his daughter-in-law is “a typical American” and “a nice lady” who also never showed any signs of radicalism.

Seddique Mateen told ABC News he’s unsure of his son’s possible motive for the attack at Pulse nightclub, which bills itself on its website as "Orlando's Premier Gay Night Club." He said he and his wife raised their children to always be accepting of others.

“I didn’t raise him that way,” Seddique Mateen said. “We gave him enough love and care and education that he knew better.”

Omar Mateen started taking hostages shortly after he entered Pulse nightclub, according to officials. He later died in a gunfight with a SWAT team, authorities said.

Law enforcement officials said the shooter called 911 to pledge his allegiance to the Islamic State group after the attack began. ISIS supporters have cheered the massacre online and an ISIS communique referred to the shooter as an ISIS "fighter," but there’s no evidence that the jihadist group directed or had prior knowledge of the attack, terrorism observers told ABC News.

"At this time we're looking at all angles right now," an FBI official said. "We do have suggestions that that individual may have leanings towards that, that particular ideology. But right now we can’t say definitively, so we’re still running everything around.”

The Florida Department of Law Enforcement is investigating Sunday morning's shooting as "an act of terrorism." It said it will determine whether it is "domestic or international" terrorism.

ABC News’ Shahriar Rahmanzadeh and Carol McKinley contributed to this report.