Officer Jeffery Westerfield, 47, was shot and killed in the 2600 block of Van Buren Street.
A police spokeswoman said Westerfield was found early Sunday after a concerned citizen called police and reported an officer bleeding in his car. Spokeswoman Cpl. Gabrielle King says Westerfield was pronounced dead at the scene.
She says investigators don't know why he was shot or who was responsible. She says it's not clear how many times he had been shot.
King says the 18-year-veteran was working the midnight shift.
She says Westerfield was found at 26th and Van Buren Streets in a residential area. That's about a block south of Roosevelt High School.
Officials said they had three men in custody, and charges are pending.