Greg Toppo

USATODAY

As investigators on Monday scoured the details of Orlando nightclub shooter Omar Mateen's life, several regulars at the Pulse nightclub offered a startling revelation: They had seen Mateen there before, they said, drinking, arguing and talking about his family.

The FBI late Monday told USA TODAY that it was reviewing these eyewitness accounts, but that it wasn't clear whether Mateen's possible visits may have served as efforts to scout the target or whether he was a patron of the club. Orlando Police Chief John Mina on Monday said he had no information about the sightings.

Pulse patron Kevin West said the 29-year-old Mateen even messaged him on and off for a year before the shooting, using a gay chat and dating app called Jack’d, the Los Angeles Times reported.

West said he was dropping off a friend at the club around 1 a.m. Sunday, an hour before the shooting, when he noticed Mateen, whom he knew by sight, crossing the street, wearing a dark cap and carrying a cellphone, according to the paper.

“He walked directly past me. I said, ‘Hey,’ and he turned and said, ‘Hey,’” and nodded his head, West said. “I could tell by the eyes,” the Times reported.

An hour later, Mateen, wielding a 9-mm semiautomatic pistol and .223-caliber rifle, killed 49 people and injured 53 before police shot him dead.

FBI: Orlando gunman not directed by foreign terror group

A federal law enforcement official who is not authorized to comment publicly said late Monday that the FBI was aware of witness reports that placed Mateen at the club on prior occasions and that the bureau was reviewing those accounts.

Another patron, Ty Smith, who also uses the name Aries, told the Orlando Sentinel he'd seen Mateen at the club at least a dozen times.

"Sometimes he would go over in the corner and sit and drink by himself, and other times he would get so drunk he was loud and belligerent," Smith said. "We didn't really talk to him a lot, but I remember him saying things about his dad at times. He told us he had a wife and child."

Chris Callen, another Pulse customer, told the Sentinel he'd seen Mateen in the nightclub and had witnessed his violent outbursts.

"It was definitely him," said Cord Cedeno. "He'd come in for years, and people knew him."

Orlando victims: Their stories

West told the Los Angeles Times that after the shooting, as soon as he saw released photos of Mateen, he went straight to police and turned over his phone and Jack’d log-in information to the FBI.

FBI Director James Comey said investigators were looking at the possibility that Mateen had also scouted Walt Disney World in April as a potential target, the Associated Press reported.

Contributing: Kevin Johnson, USA TODAY. Follow Greg Toppo on Twitter: @gtoppo