Police in Stockton, Calif., say a 15-year-old boy has died and eight people wounded in a shooting at a backyard birthday party.

Police say at least one person in an adjoining backyard opened fire on a group of people attending the party around 11 p.m. Saturday. Police Lt. Jim Pickens says the teen died in a hospital Sunday.

Eight other people hit by gunfire included six adult males, one adult female and a male juvenile. Their conditions are not known.

Pickens says detectives have determined that a neighbor was not responsible for the shooting, but rather a gunman, or gunmen, who went into the backyard and opened fire.

No arrests have been made, and police have not determined a motive.