A gunman opened fire at a live-streamed video game tournament in Florida on Sunday, killing two before turning the gun on himself.

Eleven others were shot and wounded at Jacksonville Landing, a waterfront dining, entertainment and shopping site in the city's downtown, while at least two others were injured while fleeing the scene.

Sheriff Mike Williams said police believed the suspect was David Katz, a 24-year-old from Baltimore, who used at least one handgun.

"There were three deceased individuals at the scene, one of those being the suspect, who took his own life," Sheriff Mike Williams told a news conference

"There were nine victims transported by JFRD (local fire and rescue) to area hospitals. Some of those have gunshot wounds. There were two additional gunshot victims that self-transported themselves to local hospitals."

He said authorities were still making final confirmation of his identity with the FBI assisting them in Baltimore.