The gunman involved in Saturday’s synagogue shooting at Poway, California that left one dead and three injured has been identified as 19 year old John Earnest.

San Diego County Sheriff Bill Gore said investigators were examining a "manifesto" the gunman apparently left behind on social media along with other "digital evidence."

Gore also said police and FBI were investigating Earnest's "possible Involvement" in an unsolved arson fire at a nearby mosque about a month ago.