SAN DIEGO (KGTV) - A San Diego Police officer was injured Monday in a rollover crash on Interstate 15.

The crash happened just before 1 p.m. on south I-15 just south of Adams Ave.

Authorities say the officer was transporting a prisoner on I-15 south when it hit a center median, crossed all lanes on the interstate and went up the freeway's embankment.

Police say the officer may have suffered an unknown medical issue which affected his ability to drive.

A passerby stopped to help the officer and prisoner before emergency personnel arrived on scene and were able to give medical treatment.

“I don’t know he if had a seizure of something but he hit the barricade on the left side and he swerved all the way to left side of the highway,” said Dejon Thomas, "I told my wife to stop and me and a couple of guys yanked the officer out."

Thomas, a SDGE employee, went from being a a post-lunch commuter to incidental first responder.

“We had no idea there was a guy in the backseat," added Thomas, "we just did what we could until responders came.”

Following the crash, both the officer and suspect were transported to the hospital.

The exact circumstances of the crash are unknown at this time.

Officials say both the officer and the suspect are expected to make a full recovery.