A police patrol car drives through a residential neighborhood in St. Petersburg, Fla., on Sept. 9, 2017. (Brian Blanco/Getty Images)
The shooting occurred on a Broward County Transit bus just outside the Fort Lauderdale police headquarters, but no officers were involved in the shooting, police said on Twitter.
One victim was pronounced dead at the scene, and the second died at the hospital, police said. The two others remained at the hospital.
Three other people were injured when the bus crashed into their car, officials said. They were treated at the scene.
Police said the shooter was in custody and did not believe there was any further threat to the public.