David Katz has reportedly been identified as the gunman who opened fire during a Madden NFL 19 video game tournament in Jacksonville, leaving four dead, including the suspect.

Rick Levanthal of Fox News reported that sources named David Katz was the Jacksonville shooting suspect. Police had not yet officially confirmed the suspect’s identity in the hours after the shooting.

The shooting took place at a video game tournament for Madden NFL 19 at The Jacksonville Landing, a popular entertainment complex in the Florida city. The event was being held inside the complex at the GLHF Game Bar in Chicago Pizza. The Jacksonville Sheriff’s Department confirmed that suspect identified as David Katz was dead at the scene, and they initially searched whether there were any other shooters before reporting that the suspect had acted alone. He reportedly took his own life.

The Los Angeles Times reported that the suspect was competing in the Madden NFL 19 tournament and had lost a match.

“The shooter was a gamer who was competing in the tournament and lost, according to Steven ‘Steveyj’ Javaruski, one of the competitors,” the report noted. “The shooter ‘targeted a few people; and shot at least five victims before killing himself, Javaruski told The Times in a direct message on Twitter.”

Javaruski said that he saw the suspect kill two or three people. Eyewitnesses at the tournament reported on Twitter that David Katz had just lost a match before the shooting begun.

According to the event’s Facebook page, it was a $5,000 tournament where the winner could qualify for a national tournament sponsored by Electronic Arts, the company that makes the Madden NFL series. EA Sports posted a statement after the shooting saying they were working with local authorities.

“We are aware of an incident at a sanctioned Madden Championship Series competition in Jacksonville. We are working with authorities to gather facts at this stage.”

Jacksonville Landing mass shooting leaves 'multiple fatalities,' suspect dead: police https://t.co/G1OwmYd1bp — Carl Davenport, Jr (@crlbe) August 26, 2018

Prior to Sunday’s mass shooting in Jacksonville, a number of professional gamers had complained about a lack of security at events, which were often crowded and chaotic. Just one day before the mass shooting, video showed an argument at the Madden event that nearly turned violent, with loud shouts and arguing.

Jacksonville shooter David "Bread" Katz

"He's not hear to make friends" pic.twitter.com/uksPmfvRaU — lewis (@lewisvjackson) August 26, 2018

Congrats to David Katz, the Madden 17 Bills Championship winner!



Thanks for following along, Bills fans. https://t.co/YHJHzlFElc pic.twitter.com/incdEhLxkT — Buffalo Bills (@buffalobills) February 27, 2017

Sunday’s shooting was also captured on livestream video. It did not capture the actual shooting itself, but did have audio of the moment that gunshots rang out. The video can be seen here, but be warned that it may be disturbing for some viewers.

Reports indicated that Jacksonville shooting suspect David Katz was a regular on the Madden NFL competitive tournament series, and he won a 2017 tournament sponsored by the Buffalo Bills.