Authorities were looking for a hitchhiker who stabbed a man Saturday night after being picked up near Guerneville, a sheriff's spokesman said.

The attack happened on River Road at about 7:30 p.m., Lt. Tim Duke said.

Duke said the man, whose name was not released, was driving with a child near the Stumptown Brewery when he stopped for the hitchhiker.

The hitchhiker was known only by a nickname. Duke would not release it.

At some point and for unknown reasons, the hitchhiker began stabbing the man, Duke said.

The driver was able to stop the car near Mirabel Road and get the hitchhiker out, Duke said.

He then used a cell phone to call a friend who advised him to drive to Santa Rosa, Duke said.

The man made it to Guerneville Road near the Coddingtown Mall, where he called police, Duke said.

He was taken to a local hospital to be treated for stab wounds in two places, Duke said.