Forty-nine people are dead and at least 53 injured in the deadliest shooting in American history after Omar Mateen, a 29-year-old U.S. citizen, opened fire and took hostages inside the Pulse gay nightclub in Orlando, Fla.

What we know:

Orlando shooter frequented the club where he killed 49 people and used gay dating app, witnesses say

The gunman who carried out Sunday's massacre at a gay nightclub in Orlando had been a customer there many times and used a gay dating and chat app, according to people who frequented the club.

Kevin West, a regular at Pulse, said Omar Mateen messaged him sporadically over the last year using the app Jack’d.

But they never met – until early Sunday morning.

West was dropping off a friend at the club when he noticed Mateen crossing the street wearing a dark cap and carrying a cellphone at about 1 a.m., an hour before the shooting.

“He walked directly past me. I said, ‘Hey,’ and he turned and said, ‘Hey,’” and nodded his head, West said.

At least four regular customers of Pulse told the Orlando Sentinel on Monday that they believe they had seen Mateen there before.

"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," said Ty Smith, who also uses the name Aries.

He saw Mateen at the club at least a dozen times, he said.

"We didn't really talk to him a lot, but I remember him saying things about his dad at times," Smith said. "He told us he had a wife and child."

As soon as West saw photos released of Mateen after the shooting, he said, he drove to his local police station, where FBI officials showed him a photo of Mateen on a computer screen. “I said, ‘That’s him,’” West said.

He said he turned over his phone and Jack’d login to the FBI and as of late Monday still had not received it back.

Latest updates

Copyright © 2017, Los Angeles Times