The incident occurred near 94th Avenue East and 136th Street East around 3:30 p.m.
Pierce County Det. Ed Troyer said the incident began seven blocks away at 136th and Median, where a silver car was involved in a shooting. The silver car then fled the scene, and struck the bumper of the school bus.
No one was injured in the crash. Approximately 20 children were aboard the bus at the time.
Investigators originally believed the bus had been struck at least once, but later corrected their report.
Detectives are now working to identify and track down the silver car involved in the incident. No detailed description was available.
Investigators provided no details about the shooting.