At least three people have been killed, including the gunman, and another 11 injured after the attack at Jacksonville Landing yesterday.
The massacre took place at a restaurant at a waterfront dining, entertainment and shopping site in downtown Jacksonville.
The business was live streaming a tournament for a Madden football video game when several shots rang out.
In the video, players can be seen reacting to the gunfire and cries can be heard before the footage cuts off.
David Katz, a white male, has been named by police as the suspect responsible for the massacre.
One Twitter user, Drini Gjoka, said he was taking part in the tournament and was shot in the thumb.
«Worst day of my life,» Gjoka wrote on Twitter. «I will never take anything for granted ever again. Life can be cut short in a second.»
Another gamer, Chris «Dubby» McFarland, was hospitalised after a bullet grazed his head.
He said on Twitter: «I feel fine, just a scratch on my head. Traumatized and devastated.”