Dozens of people were attending a Madden 19 event at the Jacksonville Landing when suspect David Katz of Baltimore began shooting around 1:45 p.m. Sunday.
The event was going on at the GLHF Game Bar, which is next to the Chicago Pizza at the Landing.
Event organizers said, "This is a horrible situation, and our deepest sympathies go out to all involved."
At least one suspect is dead, JSO said. Sources say four people were killed and at least 11 injured.
Video taken from the scene captured the sound of multiple gunshots as two players were engaged competition.
The two-day event is a series of competitions held in major cities.
A gamer and witness told reporter Ryan Nelson, the suspect was a gamer in an intense match.
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