The shooting was reported around 7 p.m. in the area of Pats Ranch Road and 68th Street, just east of the 15 Freeway, according to the Riverside County Sheriff's Department.
No deputy was injured in the shooting, and they did not return fire.
A large law enforcement presence swarmed the area as heavily armed SWAT officers and BearCats responded.
The alleged gunman fled on foot and officers from the California Highway Patrol, Riverside police and sheriff's deputies focused their search in the nearby Santa Ana riverbed and along the Goose Creek Golf Club Course.
The public was asked to avoid the area.