David Katz, 24, killed himself and two others, and left 11 people injured in the shooting at the Jacksonville Landing complex in Jacksonville, Florida at around 1.34pm on Sunday, police said.
According to friends in the gaming community, the two men whom Katz killed in the tournament were Taylor 'SpotMePlzzz' Robertson, 27, of Ballard, West Virginia and Eli 'Trueboy' Clayton, 22, of Woodland Hills, California.
The match was also Live Streamed on Twitch and you could hear on the stream when gunshots rang out and started to hear cries of pain and horror.