Authorities believe that 24-year-old David Katz, of Baltimore, was in Jacksonville for the Madden NFL 19 tournament at the Chicago Pizza in the downtown riverfront complex this past weekend.
Jacksonville Sheriff Mike Williams said Katz opened fire and killed two people, wounded nine others, and then turned the gun and shot himself to death.
Williams said Katz used at least one handgun in the shooting.
A motive for the shooting wasn't revealed, but witnesses told reporters the shooter had been eliminated from the tournament.
Katz went by the gaming name "Bread" and previously won Madden tournaments in 2017.
In February 2017, the Buffalo Bills shared a picture of Katz on Twitter after he won the Madden NFL 17 Bills championship.
The gunman's father is an employee of NASA, according to an agency spokesperson. Richard Katz, an engineer, works in the Instrument Electronics Development Branch, which is part of the agency's engineering directorate