Here's how first responders in Ventura County train for an active shooter

During an Aug. 8 training session, Ventura County Sheriff's deputies enter a room at Westlake High School to clear it of suspected active shooters and to help medical responders look for and treat survivors.

During a mass shooting training session at Westlake High School Aug. 8, Ventura County Sheriff's deputies enter the school theaer to clear the room of suspected active shooters and to help medical responders look for and treat survivors.

During an Aug. 8 mass shooting training session at Westlake High School, Ventura County Sheriff's deputies take down another officer posing as an active shooter.

During an Aug. 8 active shooter training session at Westlake High School, Ventura County Sheriff's deputies wait to rotate into the scenario.

During an Aug. 8 mass shooting training session at Westlake High School, Ventura County Sheriff's deputies enter the school theater to clear it of suspected active shooters and to help medical responders look for and treat survivors.

During an Aug. 8 mass shooting training session at Westlake High School, a Ventura County firefighter medically assesses county fire engineer Jason May, who is posing as a shooting victim.