Authorities on Sunday were continuing to investigate reported gunfire the night before at a Sebastopol Road auto body shop where people had gathered for a party.
Dozens of law enforcement officials converged upon Acme Automotive at about 9:45 p.m. Saturday after a person called 911 to report that people were shooting at one another.
People interviewed at the scene said about 50 people were attending some type of birthday celebration at the automotive shop, and that guests included young children.
Deputies interviewed an uncooperative woman who had blood on her dress but no wounds. Nearby, authorities found an expended shell casing.
Party-goers confirmed a shooting had occurred but they offered no additional information, according to Sonoma County Sheriff's Lt. Tim Duke. Authorities were investigating it Sunday as an assault with a deadly weapon.
The sheriff's Violent Crimes Investigation Unit took over the investigation.
Anyone with information is asked to contact the Sheriff's Office at 565-2185.