By Evan Perez, Shimon Prokupecz and Holly Yan CNN

(CNN) -- Authorities believe the gunman who killed 49 people at Orlando's Pulse nightclub conducted surveillance trips at both the club and a Disney entertainment and shopping complex this month, a law enforcement official said Tuesday.

Omar Mir Seddique Mateen's visits at Pulse and Disney Springs happened between June 1 and June 6, said the official, who has knowledge of the investigation. The number of visits to each venue was not specified.

The dates coincided with Gay Days 2016 celebrations taking place at Walt Disney World and other Orlando locations between May 31 and June 6.

Investigators believe the visits were intended to surveil the locations, based on information learned in interviews.

The visits also came in the same time period when Mateen was purchasing the weapons used in Sunday morning's nightclub attack.

The day before that rampage -- the deadliest mass shooting in U.S. history -- Mateen spent several hours at Disney Springs, formerly known as Downtown Disney, law enforcement officials said.

Authorities said they believe Mateen was alone at that time.

Earlier Disney visit with wife

Disney security officials have told the FBI they believe that Mateen made another visit to Disney World on April 26 to conduct reconnaissance, the law enforcement official said.

The FBI is investigating that possibility.

Investigators don't know whether Mateen's wife, who was with him on the Disney World visit, knew or suspected at the time about her husband's intent, the official said.

Items seized from homes

The FBI has seized documents from Mateen's home as well as items from the homes of his parents, sister and brother-in-law, the law enforcement official said.

The items included a Dell computer, a smartphone, a digital camera and related media.

Mateen's phone was recovered at Pulse. FBI Director James Comey would not say Tuesday whether authorities have accessed the phone.

Conflicting persona

To some, Mateen was angry and homophobic, reportedly spewing outrage at the sight of two gay men kissing.

But he was also a friendly and familiar face at the gay club he eventually terrorized, killing 49 people.

Chris Callen, who worked at Pulse as a performer, told CNN's Anderson Cooper he had seen Mateen dozens of times at the club. According to Callen's estimate, Mateen visited Pulse twice a month over a period of 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."

Pulse regular Kevin West told the Los Angeles Times that Mateen messaged him on a gay dating app several times in the year before the attack.

But that picture doesn't match up easily with accounts from colleagues who said Mateen was known to make anti-gay remarks frequently.

"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-TV in West Palm Beach. Mateen and Gilroy had worked together at PGA Village in Port St. Lucie

Gilroy said Mateen had a temper and often made homophobic, sexist and racist remarks.

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

He said he wished he could have done something to prevent the tragedy.

"I saw it coming. I mean everything," he said. "He said he was going to kill a whole bunch of people."

Ex-wife: He abused me

Mateen's first wife, Sitora Yusufiy, painted a damning portrait of the killer, describing a physically abusive marriage to a man with anger issues.

Yusufiy, who is originally from Uzbekistan, said the relationship started well after they met online about seven years ago.

"In the beginning, he was a normal being that cared about family, loved to joke, loved to have fun, but then a few months after we were married I saw his instability," she said.

"He would get mad out of nowhere. That's when I started worrying about my safety."

She said the abuse became a regular occurrence.

"He started abusing me physically, very often, and not allowing me to speak to my family, keeping me hostage from them," Yusufiy said.

"(My family) had to pull me out of his arms and find an emergency flight. ... I made a police report."

While her ex-husband was religious, Yusufiy said, she did not believe his religion played a role in the nightclub attack.

Married with a child

Mateen lived in a condo in Fort Pierce, Florida, with his second wife, a woman named Noor Salman, according to documents CNN obtained.

He also had a 3-year-old son, according to Mateen's father.

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.

FBI had investigated him twice

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 was able to purchase a handgun and assault rifle legally in the days before the massacre, said Trevor Velino of the Bureau of Alcohol, Tobacco, Firearms and Explosives.

'A hell of a lot of jihadist propaganda'

Comey, the FBI director, said the bureau is "highly confident" Mateen was radicalized, at least in part, by viewing extremism on the Internet.

"There are strong indications of radicalization by this killer and of potential inspiration by foreign terrorist organizations," Comey said.

He said investigators have found no indication the attack was directed from outside the United States or that Mateen was part of any kind of network.

According to one official, analysis of Mateen's electronic devices showed searches for jihadist propaganda, including videos of ISIS beheadings.

"He consumed a hell of a lot of jihadist propaganda," the source said.

Father baffled by killings

But 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."

CNN's Tiffany Ap, Catherine E. Shoichet, Pamela Brown, MaryLynn Ryan, Vivian Kuo, Samira Jafari, Patricia DiCarlo, Salma Abdelaziz, Scott Glover, Jackie Wattles, Christine Sever and Joshua Gaynor contributed to this report.

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