Pleasant Hill officers on Monday responded to a multiple-vehicle collision in which one of the cars, a Cadillac, was ripped in half, police said.
The driver of the Cadillac fled the scene on foot and was found bleeding in a nearby residential neighborhood, police said.
The crash, which occurred at Taylor Boulevard and Pleasant Hill Road, reportedly involved at least three vehicles. Police said the Cadillac was speeding down Taylor before it hit two other vehicles and slammed into a light pole, shearing the car in two.
The suspect was suffering from stab wounds in his neck and back and was taken to a hospital with major injuries. No details were given on his condition.
Resident Mike Carlson was talking to a friend in his living room when they saw a man covered in blood in his backyard.
"I turn around, and the guy is in my backyard and looks like he's trying to jump the fence, covered in blood," Carlson said.
He said police swarmed his yard before he could call 911.
"They had a gun on him asking him who stabbed him," Carlson said. "I'm thankful my kids weren't here."
Pleasant Hill police believe the man was stabbed in Martinez, and they are currently working with the Martinez Police Department in a joint investigation.
Two occupants of other vehicles involved in the crash suffered minor injuries, police said.