Officers from Marine Corps Logistics Base Barstow, Calif. police department prepare for an active shooter training exercise at the MCLBB Security and Emergency Services training facility on November 18. The exercise used simulated ammunition in order to allow participants to use their duty weapon while combating opposing force personnel. - Officers from Marine Corps Logistics Base Barstow, Calif. police department prepare for an active shooter training exercise at the MCLBB Security and Emergency Services training facility on November 18. The exercise used simulated ammunition in order to allow participants to use their duty weapon while combating opposing force personnel.