The shooting happened shortly after 3:00 p.m. on Erie Avenue near Broad Street.
Police say someone opened fire on a man, striking him in the buttocks.
During the burst of gunfire, police say, one projectile struck the Septa Route 56 bus, but no one on the bus was struck.
However, the driver of a car in the proximity lost control and struck the bus.
There was no immediate word on any injuries in crash.
There have been no arrests in the shooting.