A man on his motorcycle was killed Saturday night after he was run over by a bus.

It happened just after 7 p.m. on Saturday at the intersection of West Theo and De Soto.

Police said a VIA bus was headed northbound on DeSoto when a motorcycle rider, headed westbound on Theo, laid down his bike and ended up under the front tire of the bus.

Police said the rider was not wearing a helmet and while they are investigating and looking at the speed, they said it's really not clear what caused the accident.

"There were no bus riders, no witnesses," said  Sgt. Roberto Reyes with the San Antonio Police Department. "We just have to depend on the evidence that we have to determine what happened."

Reyes said the south-side area is common for accidents and that just 5 months  ago, another  motorcycle rider was killed after hitting a van.

A spokesperson for VIA said that the bus driver was not injured and that there were no passengers on the bus at the time, but that they will be conducting some "post accident testing," which is standard procedure.

The name of the rider has not been released, but police said he was 37 years old.