The male pedestrian was struck around 10 p.m. at West Third Street and Stony Point Road by a vehicle driven by 22-year-old Kevin Tarara, Sgt. Lance Badger said.
Witnesses told police the pedestrian was running in and out of the roadway and removing his clothing, and that he was in Tarara's lane of traffic when he was struck, Badger said.
The pedestrian was taken to Santa Rosa Memorial Hospital, Badger said.
Police do not yet know if drugs or alcohol played a role in the incident, Badger said.
