Yvonne Scott, 58, of the 6500 block of North Gratz Street, was a passenger in the car involved. She was also the aunt of the driver, a 31-year-old woman.
It happened just after 6:00 p.m. Monday along the 6100 block of Old York Road near Sparks Street.
Witness Maurice Bowman tells Action News he was traveling southbound on Old York Road just before the accident when he noticed the woman in an Acura traveling northbound swerve into his lane.
"She was coming down, she was kind of in my lane so I swerved out the way and I looked in my rearview mirror and she just ran into the bus," Bowman said.
Firefighters, who at the time were passing through, stumbled onto the accident scene with 55 people onboard the SEPTA bus.
"Actually we were responding to another call and Ladder 29 came upon this accident which wound up being a Level 5 mass casualty incident," Battalion Chief Derrick Sawyer of the Philadelphia Fire Department said.
Officials say the driver of the Acura was taken to Albert Einstein Medical Center where she is in critical condition.
Scott was pronounced dead at the scene.
Police say 11 people onboard the bus, including the bus driver, were injured.
"They're all walking wounded which is complaints of pain, stiffness, things of that nature," Chief Inspector Scott Small of the Philadelphia Police Department said.
All 11 were taken to three area hospitals where they were treated and released.
Resident Angela Holloway tells Action News she was sitting in her parked car when the accident happened just a few feet away.
"It was terrible, it was really terrible and I was shocked," Holloway said.
Neighbor Warren Young described the scene as a chaos.
Investigators say it appears the driver of the Acura was driving in the wrong lane when it collided with the bus.
Authorities tell Action News they are looking into the possibility that the 31-year-old driver was under the influence.
"There was strong odor of alcohol coming from the Acura, it also had open containers of alcohol inside of that vehicle," Small said.
Police say the bus is equipped with interior and exterior cameras which caught the incident, but it is up to SEPTA to decide whether or not to release the video.