Officers with Marine Corps Logistics Base Barstow’s Marine Corps Police Department practice clearing during an active shooter exercise here, April 9. The purpose of the training was to hone and develop MCPD officer’s skills on responding to active shooter incidents. - Officers with Marine Corps Logistics Base Barstow’s Marine Corps Police Department practice clearing during an active shooter exercise here, April 9. The purpose of the training was to hone and develop MCPD officer’s skills on responding to active shooter incidents.