A terrifying livestream video shows the moment just before one of the victims was fatally shot at the Jacksonville Madden tournament. Jacksonville Police identified 24-year-old David Katz as the suspected gunman in the shooting, which left three people — including Katz — dead and 11 wounded.

According to the Tampa Bay Times, Twitter users and fellow gamers suspected Katz was upset about losing two games of Madden earlier in the tournament. After his losses, he refused to shake hands with the winner after at least one game.

"He’s a well-known competitor," said one gamer to WFOX-TV, who claimed to have beaten Katz on Saturday. "[He was here] all weekend. He had shades on, he didn’t speak to anybody. Even after we played … I went to shake his hand and just tell him good game and he just looked at me. He didn’t say anything."

Police say Katz carried out the shooting with a handgun, although a semi-automatic weapon was also found at the scene.

Last year, Katz won the Madden Bills Championship.

Moments before the shooting on Sunday, a recording on livestream platform Twitch showed 22-year-old Eli “TrueBoy” Clayton, one of the victims, smiling while playing. Some people noticed there was a red dot on his chest, yet police haven’t confirmed if it was related to the shooting.

The other fatal victim was Taylor “SpotMeplzzz” Robertson, 27, an avid gamer who had a wife and son.