The Dallas Police Department union reports a fifth officer has died.
The DART officer killed was Officer Brent Thompson, 43, the first DART officer killed in the line of duty. He has been with DART since 2009.
Five other officers and a civilian have also been shot and are at Baylor and Parkland hospitals.
Three people are in custody and a fourth, who was in a standoff with police at El Centro garage, has been arrested.
Channel 8 was reporting a sixth officer killed, but that information was incorrect.