(CNN) Investigators believe the Orlando nightclub gunman made surveillance trips to the club and a Disney shopping complex earlier this month -- the same week Disney and other sites were hosting Gay Days 2016.

Omar Mir Seddique Mateen's visits to the Pulse gay nightclub and Disney Springs happened between June 1 and June 6, a law enforcement official said Tuesday. Gay Days 2016 celebrations took place at Walt Disney World and other Orlando locations between May 31 and June 6.

A law enforcement official said the gunman's wife, Noor Salman, went with her husband to the two locations. It's unclear how much she knew about his intentions.

Mateen had showed an aversion toward gays -- making inflammatory remarks and expressing outrage at the sight of two men kissing, law enforcement officials and a former co-worker said.

But sources say he visited gay chat rooms and for years frequented the same nightclub that he would eventually terrorize.

Was the mass shooting fueled by homophobia? Was the gunman struggling with his own sexuality? Or was he really inspired by ISIS, as his mid-rampage call to 911 suggests?

Authorities are investigating many angles to try to understand what prompted him to carry out the deadliest mass shooting in U.S. history. A total of 49 people were killed early Sunday and 53 people were wounded. Officials said that 28 victims are still hospitalized, including at least four people who are in critical condition.

Here's what we know about the gunman:

Scouting out Disney World, Disney Springs

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Disney security officials told the FBI they believe Mateen visited Disney World on April 26 to conduct surveillance, a law enforcement official told CNN. The FBI is investigating that possibility.

Mateen's wife also was with him on the Disney World visit. Federal authorities have questioned Salman, who told them, according to a law enforcement official, that her husband had talked about a jihadist attack but she denied knowing he planned to attack the gay club.

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More than a month after that Disney World trip, 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. Authorities believe he was conducting surveillance, based on information learned in interviews.

The early June visits took place during the same period Mateen was purchasing the weapons used in the devastating attack.

Hours before the carnage, Mateen made one last trip to Disney Springs, law enforcement officials said. That time, Mateen was alone.

Conflicting persona

Officials say they're looking into the possibility Omar Mateen radicalized on his own.

To some, Mateen was a homophobic "bigot." To others, he was a friendly regular at the nightclub.

Chris Callen, who worked at Pulse as a performer, said he had seen Mateen dozens of times. According to Callen's estimate, Mateen visited Pulse 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."

Mateen visited gay chat rooms online, two law enforcement officials said. Investigators do not know whether he visited the chat rooms for surveillance purposes ahead of the attack or for personal reasons.

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The FBI is 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 Mateen.

On the other hand, a former colleague said Mateen often made homophobic, sexist and racist remarks.

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"He was an angry person, violent in nature, and a bigot to almost every class of person," former co-worker Dan Gilroy told CNN affiliate WPTV . Mateen and Gilroy had worked together at PGA Village in Port St. Lucie.

Gilroy said Mateen had a temper.

"He would hit things and as he was hitting things, he would yell, and of course there was always curse words involved," Gilroy told WPTV. "And this wasn't seldom, this was all the time."

And Mateen's ex-wife, Sitora Yusufiy, says he was often violent, abusive and prone to outbursts, including one instance where she was on the phone with her mother and was slapped so hard the phone broke.

As questions about Mateen's sexual orientation arise, Yusufiy admitted she does not know if he is gay or not.

"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 said in an interview with CNN's Don Lemon. "I hope people can truly understand that this is one insane person that did such a tragic thing."

FBI had investigated him twice

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Mateen first came on the FBI's radar in 2013 when he made "inflammatory comments to co-workers alleging possible terrorist ties," Assistant Special Agent in Charge Ronald Hopper said. But investigators "were unable to verify the substance of his comments," he said.

In 2014, the FBI interviewed Mateen 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.

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.

Sheriff Ken Mascara said that in 2013 his staff requested Mateen be transferred from the courthouse because he made inflammatory comments. Mateen's supervisor notified federal agents, after which, the sheriff said, the FBI investigated the guard.

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, Mateen 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.

Mateen also achieved an above average rating on a psychological test.

During the gunman's rampage, he called 911 and pledged allegiance to ISIS, a U.S. official said. Mateen also mentioned the Boston Marathon bombers.

An analysis of Mateen's electronic devices showed searches for jihadist propaganda, including videos of ISIS beheadings, an official said.

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After meeting with national security officials Tuesday, President Barack Obama said there is no indication a foreign terror group directed the Orlando massacre. But he conceded that "these lone actors or small cells of terrorists are very hard to detect and very hard to prevent."

Father baffled by killings

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Mateen's father, Seddique Mateen, said he had no idea his son was about to commit an act of mass violence.

"I am as shocked as you are," he told CNN.

The father had an occasional television show on an Afghan satellite channel in which he regularly criticized Afghanistan's government and Pakistan.

Seddique Mateen said he doesn't believe religion motivated his son's attack.

"Radicalism? No. He doesn't have a beard even. When someone becomes radical, they grow long beards and they wear clothes that you know, long clothes, and I don't think religion or Islam had nothing to do with this," he said.

He said his son may have pledged allegiance to ISIS because "he wanted to boost himself."

But the father condemned the terror group.

"The way they conduct themselves, they're harming everybody. They're not a religious group. I don't know what they are," he said. "They're a killer group."