The accident happened around 2:10 p.m. at Moss Rehab in the 9800 block of Bustleton Avenue.
Rescuers tell Action News that a vehicle hit the man and pinned him against a building.
Witnesses say there were several medical assistants sitting out front, taking a break, when the accident happened. They were able to jump into action and help the victim.
Donna Miller was on the second floor when she felt the crash, looked out her window, and saw the scene.
"All we felt was a bang and we felt building shake. We looked out and saw there was a car through the front there," she said. "I couldn't believe how that happened, to be quite honest."
Police say the driver, who is in his 70s, accidentally hit the gas and rammed the building, striking the man in the wheelchair.
The man who was hit suffered a leg injury, possibly a fracture. He is in stable condition.
The driver and his female passenger were also taken to the hospital to be checked out.
"To be in a wheelchair and he's here to make himself better to get out of the wheelchair, then he gets hit? I hope all goes well for him," said Miller.
Criminal charges do not appear likely.
An investigation continues into this accident.
