Katz killed two people and himself after shooting up the Jacksonville tournament following his loss.
David Katz showed zero emotion as he played in a tense tournament against other professional gamers prior to Sunday’s mass shooting inside a Florida mall.
The 24-year-old was an elite player of the video game "Madden NFL 19" and was known by the tag name “Bread.” He was also known as “MrSlicedBread,” and “RavensChamp.”
He wore the same blank expression whether he won or lost.
A live stream from the tournament captured audio of the chaos that followed on the streaming service Twitch.
The victims were identified as Elijah Clayton, 22, and Taylor Robertson, 27.
Esports can draw enormous crowds. Last month, more than 20,000 people attended a showdown at Brooklyn’s Barclays Center.
Gamer Rod Bresley spoke to Inside Edition about the popularity of Esports.
"You will find enormous stadiums with people — sold out, filled to the brim — watching their favorite player like you would traditional sports,” he said. "They want to watch the best players in the world."
Pro-gamers see themselves as athletes. At a recent boot camp in Texas, they work out and stick to rigid diets.
Katz won a "Madden" championship in 2017 and his intensity was on display when he was interviewed by former NFL star Steve Tasker, who asked about his placement as a No. 7 seed.
“I don't see myself as a seven seed," Katz told Tasker. "I think I’m one of the better players and I let my game prove that."