Orlando nightclub gunman Omar Mateen visited online gay chat rooms despite expressing outrage at the sight of two men kissing and making inflammatory comments about gays, law enforcement officials said.
Investigators don't know whether he visited the chat rooms for personal reasons or for surveillance before carrying out the brutal attack early Sunday at the Pulse gay nightclub in Orlando, killing 49 people and wounding more than 50 others.
Days after the attack -- the deadliest mass shooting in U.S. history -- sources revealed he not only visited gay chat rooms, he also frequented the same nightclub he would eventually terrorize.
A former colleague has said Mateen constantly made homophobic, sexist and racist remarks.
FBI agents are interviewing people who claim they met the gunman on gay dating apps, a law enforcement official told CNN's Pamela Brown. Those claims "certainly change the perspective," the source said.
No men have publicly come forward claiming to have had sexual contact with him.
Was killer gay?
Mateen's father said Tuesday he doesn't believe his son was gay.
After reports emerged his son had visited Pulse several times before the massacre, Seddique Mateen said he saw nothing implying his son was gay.
"I don't know if he was, if that was his way of his life, but I don't believe so," Seddique Mateen told reporters at his home in Port St. Lucie, Florida. He emphasized his belief that his son, who was married with a child, was straight.
The gunman's first wife, Sitora Yusufiy, said she was not sure about his sexuality.
"It doesn't surprise me that he might be gay. And it doesn't surprise me that he was leading two totally different lives and was in such deep conflict within himself," she told CNN's Don Lemon. "I hope people can truly understand that this is one insane person that did such a tragic thing."
'Bigot to almost every class of person'
People who knew the gunman painted two conflicting images. To some, he was a homophobic bigot. To others, he was a friendly regular at a gay nightclub.
Chris Callen, who performed at Pulse, estimated Mateen visited the nightclub twice a month over three years.
"He was very friendly when we said, 'Hi.' He didn't seem like the kind of guy who just did what he did. It makes no sense," Callen said. "My partner said that he was very nice (and seemed) comfortable."
In contrast, an ex-co-worker described Mateen as a man who constantly made derogatory remarks about others.
"He was an angry person, violent in nature, and a bigot to almost every class of person," Dan Gilroy told CNN affiliate WPTV-TV in West Palm Beach. The two worked together at PGA Village in Port St. Lucie.
Why the U.S. has the most mass shootings
What was gunman's motive?
Authorities are investigating multiple angles to understand what led Mateen to target people at a gay nightclub.
Was the mass shooting fueled by homophobia? Was he struggling with his sexuality? Or was he inspired by the terror group ISIS, like he said in a 911 call during the rampage?
Gunman visited sites before massacre
In the days leading up to the attack, Mateen appeared to be scouting locations.
Investigators believe he made surveillance trips to the club and a Disney shopping complex this month during Gay Days 2016, a citywide celebration. Walt Disney World and other Orlando locations held Gay Days events between May 31 and June 6.
Mateen's visits to the Pulse nightclub and Disney Springs happened between June 1 and June 6, a law enforcement official said Tuesday.
Disney security officials told the FBI they believe he also visited Disney World on April 26 to conduct surveillance, a law enforcement official told CNN.
Wife visited two locations
The gunman's wife, Noor Salman, told the FBI that Mateen said he wanted to carry out a jihadist attack, though she denied knowing of any specific plans.
She went with her husband to two locations, a law enforcement official said. It's unclear how much she knew about his intentions.
More than a month after the Disney World trip in April, Mateen and his wife visited Pulse and Disney Springs -- an entertainment and shopping complex -- apparently to scout out the locations, a law enforcement official said.
Investigators are trying to determine whether Salman should face charges for not reporting what she knew, a source said.
The early June visits occurred during the same period Mateen purchased the weapons used in the nightclub attack.
Hours before the carnage, he made one last trip to Disney Springs by himself, law enforcement officials said.
The couple lived in Fort Pierce, Florida, about an hour from the club. Salman told the FBI she noticed changes in her husband's behavior and tried to dissuade him from doing anything violent, the official said.
When he left their home Saturday, hours before the mass shooting, he lied about where he was going, Salman told federal investigators.
FBI had investigated him twice
Mateen first came on the FBI's radar three years ago, when he made "inflammatory comments to co-workers alleging possible terrorist ties," assistant special agent Ronald Hopper said.
But investigators "were unable to verify the substance of his comments," he said.
In 2014, the FBI interviewed him again over possible connections with Moner Mohammad Abu-Salha, a Florida man who became the first-known American suicide bomber in Syria. The two men frequented the same mosque.
"We determined that contact was minimal and did not constitute a substantive relationship or threat at that time," Hopper said.
Problems at work
Mateen had worked for nine years as a security officer at G4S Secure Solutions, one of the world's largest private security companies. According to a neighbor, he was a security guard at the St. Lucie County Courthouse, often manning the metal detectors at the front of the building.
St. Lucie County Sheriff Ken Mascara said three years ago, his staff requested Mateen be transferred from the courthouse because he made inflammatory comments. His supervisor notified federal agents, and the FBI investigated him, the sheriff said.
Mateen told an attorney for G4S about being questioned, an official for the security company told CNN's Rene Marsh. G4S determined Mateen's comments were "exaggerated."
By that time, he was working security at a retirement village. He had no reprimands in his file and had his security officer license renewed four times -- in each instance passing background checks by the state and FBI. He also achieved an above-average rating on a psychological test.
But the massacre Sunday was carried out by a man who appeared to be at the very least disturbed.
During the rampage, he called 911 and pledged allegiance to ISIS, a U.S. official said. He also mentioned the Boston Marathon bombers.
An analysis of his electronic devices showed searches for jihadist propaganda, including videos of ISIS beheadings, an official said.