SAN DIEGO (CNS) — An artillery shell that exploded over Interstate 5 near Camp Pendleton during an October live-fire demonstration, scattering shrapnel onto the closed freeway, was caused by a rare malfunction, according to a U.S. Marine Corps investigation.
Shrapnel from the incident landed on a California Highway Patrol vehicle and motorcycle that were part of the security detail for Vice President JD Vance, who attended the event with Secretary of War Pete Hegseth in honor of the U.S. Marine Corps' 250th birthday celebration.
The 666-page report was released Friday by the commanding general of I Marine Expeditionary Force at Camp Pendleton. The incident occurred Oct. 18 during a large-scale military demonstration on the base. Marines fired a 155-millimeter artillery round from a howitzer toward a designated training impact area when the projectile detonated prematurely in midair.
Investigators determined the likely cause was a malfunction in the shell's electronic time fuze, a component designed to control the timing of the explosion. The failure was described in the report as extremely rare, with officials saying the device has a very low historical malfunction rate.
The round exploded about 1,500 feet above ground, sending fragments downward onto a closed section of I-5 that runs along the western edge of the base. No one was injured and officials halted the exercise immediately after the explosion.
Dozens of artillery rounds had been scheduled for the demonstration, which was part of a broader training event and public showcase of Marine capabilities.
The investigation found no evidence of operator error and concluded that Marines followed approved safety procedures. The report noted that factors such as the proximity of multiple artillery guns firing in quick succession or possible electromagnetic interference could have contributed to the malfunction, though investigators could not determine a definitive secondary cause.
The event drew criticism from some California officials who questioned the decision to conduct live-fire artillery training near a major civilian transportation corridor.
Marine Corps officials said the demonstration took place within an approved training area and that safety protocols including the freeway closure functioned as intended.
The USMC said it is reviewing the findings from the closed investigation and may adjust procedures for future demonstrations conducted near public infrastructure.
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