Police say another person had arrived and possibly picked up a bag that may have contained a gun.

PHILADELPHIA (WPVI) -- A 19-year-old man accidentally shot himself on a SEPTA bus in West Philadelphia.
It happened as the bus was driving on South 60th Street, near Christian Street.
The driver reported hearing the gunshots.
By the time police arrived to the scene, the 19 year old had run away from the bus, but was quickly found.
Police said they quickly determined the 19-year-old had inadvertently shot himself.
He is hospitalized in stable condition.
Police say another person had arrived and possibly picked up a bag that may have contained a gun.
They are searching for that person right now.