The gunman from the mass shooting in downtown Jacksonville was a gamer who lost in a "Madden 19" tournament on Sunday, witness Steven Javaruski told the Los Angeles Times.
Jacksonville Sheriff Mike Williams said a lone, white male suspect was dead.
"I'm really easy to get along with, I'm not a troublemaker", he said.
UF Health Jacksonville took in six patients, four of whom were discharged from the hospital. The victims ranged in age from 20 to 35 years old. "Our most heartfelt sympathies go out to the families of the victims whose lives were taken today and those who were injured".
At least three patients were shot once, and three were shot a couple of times, UF Health said. "I have been allowed to release their names so that their families are aware that they are OK", Michael Samotowka, trauma medical director at Memorial Hospital, said.
The shooting was captured on various Twitch live streams of the event.
As the live video shot cuts to the action on the virtual football field, gunshots and chilling screams can be heard in the background.
He appears to have won the the Madden Bills Championship in 2017.
"I am still in shock", he said.
Local authorities warned residents to stay away from the area due to a mass shooting and said it was unclear whether there was a second suspect. "One of the men ran into Hooters with the shot wounds, they locked us in the restaurant", he said in a social media message. "Then we heard repeat shots and we took off running", said Mr Williams, who participated in the tournament earlier.
The incident has prompted many gamers to call for increased security at eSports events. "Love you all and hope something like this never happens again".
Florida Governor Rick Scott said he had offered state support in the aftermath, and that President Donald Trump had offered "any federal resources needed".
Jason Lake, founder and CEO of compLexity Gaming, a professional gaming company that Gjoka was a member of, said he was " cooperating with the authorities and we will be flying him out of Jacksonville as soon as we are given the green light from the officials on the ground".
The Sunday shooting immediately became an issue in Florida primary elections set for Tuesday when voters choose candidates for governor and the U.S. House of Representatives.