JACKSONVILLE, Fla. -- A gamer at a "Madden NFL 19" qualifying tournament opened fire at a restaurant in a Florida mall on Sunday, killing two people and sending 11 others to hospitals, authorities said.

Jacksonville Sheriff Mike Williams identified the shooter as 24-year-old David Katz of Baltimore. Williams said Katz died of a self-inflicted gunshot wound and that he used one handgun in the shooting at Chicago Pizza, which is located at The Jacksonville Landing.

Williams said that nine victims -- seven with gunshot wounds, two hurt fleeing the scene -- were transported to a hospital and two others with gunshot wounds drove themselves to a hospital. All were in stable condition, he said.

The Madden NFL 19 Classic qualifying tournament was taking place in the GLHF Game Bar, which is located inside Chicago Pizza. Williams said the Jacksonville Sheriff's Department received 911 calls at 1:34 p.m. ET and was on the scene at 1:36.

The tournament was being live-streamed on Twitch and a video of the event surfaced, with gunshots heard in the background. The sheriff's office said it had obtained that video.

Drini Gjoka, one of the professional gamers at the tournament, tweeted that he had been shot in the thumb.

I am literally so lucky. The bullet hit my thumb — Drini Gjoka (@YoungDrini) August 26, 2018

I will never take anything for granted ever again. Life can be cut short in a second — Drini Gjoka (@YoungDrini) August 26, 2018

Another gamer, Tim Anselimo, was shot multiple times, according to his mother.

"He was shot three times, once on the nipple, once on his hand and somewhere else," Sujeil Lopez told the New York Times.

Anselimo is a member of Bucks Gaming, the Milwaukee Bucks' NBA 2K League team.

"Our thoughts are with Tim and his family after this horrific situation," Cayle Drabinsky, Bucks director of business operations and co-managing director of Bucks Gaming, said in a statement. "We are in close contact with his mother and continue to monitor his health."

EA Sports, which produces "Madden NFL 19," expressed condolences for the victims and also condemned the shooting in a statement on Twitter.

The NFL said in a statement the league was "shocked and deeply saddened by the horrific tragedy today in Jacksonville. Our hearts go out to all those affected. We are grateful for the first responders immediately on the scene. We support our partners at EA Sports and will continue to monitor developments with local law enforcement."

Jaguars owner Shad Khan said in a statement that it was "impossible to comprehend" the news of the shooting:

"I'm heartbroken for the families and friends of the victims and can only express my deepest condolences as we try to understand why and how this can happen, not only here, but anywhere. What I can say is I know today what lifelong Jacksonville residents have known forever -- we are resilient, compassionate and remarkably supportive of our neighbors and friends, particularly in the most trying occasions. This tragedy will ask the best of all of us, but I know we will respond."

The Jacksonville Landing, in the heart of the city's downtown, hosts concerts and other entertainment, and it has a busy food court and a host of bars and restaurants.

The Associated Press contributed to this report.