Police originally gave the elder shooter's age as 19.TV footage from a helicopter showed armed response teams gathered outside a building, with one unidentified person lying in a pool of blood.Dozens of patrol cars were lined up around the Islamic Center, described on its website as the largest mosque in San Diego county, which lies in southern California.After a short period of lockdown when authorities advised residents to stay inside, San Diego police announced that the threat at the centre had been "neutralised"."We received a call of an active shooter at the Islamic centre Within four minutes, officers arrived on scene and observed immediately three deceased victims out in front," San Diego police chief Scott Wahl told reporters."We immediately began to deploy with an active shooter response into the mosque and adjacent school," he said, adding that police had received calls about more gunfire nearby, where a landscaper at work had been shot at but not hit.All of the children who were attending a day school that is part of the mosque complex were accounted for and safe after the shooting, Wahl said.He said the FBI was called in to assist in the investigation of the incident, which the police chief said authorities were treating as a hate crime.Wahl said the mother of one of the two suspects had called police about two hours before the shooting to report that her son, whom she described as suicidal, had run away from home taking three guns she owned and her vehicle.According to the chief, the mother said her son was with a companion and the two were dressed in camouflage