The man allegedly took neighbours hostage in a Hialeah apartment building for reasons that were not immediately known, said police spokesman Sergeant Eddie Rodriguez.
"Six innocent people died and also the suspect who initiated this situation," Rodriguez added.
He said the incident began at 6:30 pm, local time yesterday and ended at 2:30 am today when a police SWAT team moved into the building.
The team "entered the apartment where the suspect was holding a neighbour couple as hostages," Rodriguez said.
Rodriguez said they were the building's landlords.