Three deputies were killed Friday in an explosion at the L.A. County Sheriff’s Department’s Biscailuz Center Training Academy in East L.A., the deadliest incident for the agency in more than 160 years.

Three veteran Los Angeles County Sheriff’s Department members assigned to the agency’s arson and explosives detail were killed Friday morning by an explosion at a department training facility, according to Sheriff Robert Luna.

Three members of the arson and explosives unit of the Los Angeles County Sheriff’s Department have been killed in a blast at the department’s training facility