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 adultfyi 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.

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.”

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

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, said he’d seen Mateen at the club at least a dozen times.