Early Sunday morning, Omar Mateen shot and killed 49 people at a gay nightclub in Orlando, perpetrating the deadliest mass shooting in U.S. history. Mateen, his father explained the next day, had repeatedly been angered by the sight of two men kissing. But according to witnesses, Mateen was also a regular at the club and exchanged messages with at least one gay man on a gay dating app.

“It’s the same guy,” Chris Callen, who performs under the name Kristina McLaughlin, told the Canadian Press. “He’s been going to this bar for at least three years.”

Ty Smith, who also goes by the name Aries, also said he’d seen Mateen being escorted drunk from the club, Pulse, on multiple occasions.

“(He’d get) really, really drunk... He couldn’t drink when he was at home—around his wife, or family. His father was really strict... He used to bitch about it,” Smith told the Canadian Press.

“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 also explained to the Orlando Sentinel, which spoke with at least four clubgoers who remembered seeing Mateen at Pulse at least a dozen times. “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.”

Both Callen and Smith, who are married, tell the Canadian Press they stopped speaking to Mateen after he threatened them with a knife, apparently after someone made a joke about religion.

“He ended up pulling a knife,” Callen said. “He said if he ever messed with him again, you know how it’ll turn out.”

Mateen, who was married in 2009, was abusive and unstable, his ex-wife says. They were married for just a few months before her parents rescued her from their home in Florida, leaving most of her belongings behind. It’s still unclear if he was married again after their divorce was finalized in 2011.

MSNBC host Chris Hayes also says he spoke to a man who claims both he and a friend received messages from Mateen via a gay dating app. The full story is set to air tonight on Hayes’ show, All In.