A live artillery shell exploded too soon during a Marines live-fire demonstration in southern California on Saturday, creating a California freeway explosion that sent metal fragments onto Interstate 5. The incident happened during an event marking the Marine Corps’ 250th anniversary at Camp Pendleton, north of San Diego.
Officials said the explosion caused shrapnel to rain down on vehicles parked along the closed freeway, including a California Highway Patrol car and a motorcycle in the security detail of Vice President JD Vance. No serious injuries were reported, but the event sparked alarm among state leaders over public safety and military oversight.
According to a police report, the 155mm shell detonated before reaching its target area. Fragments struck several vehicles on a ramp near the highway, leaving dents and marks. Officers described hearing the sound of small objects hitting their motorcycles and cars, while pieces of metal were found scattered nearby.
The California Highway Patrol had closed a 17-mile stretch of the busy Interstate 5 before the exercise. The decision came early Saturday morning after state officials learned that military planners had not initially intended to shut down the freeway. The closure caused long traffic jams across the San Diego-Los Angeles corridor.
Following the California freeway explosion, the Marines canceled the remaining part of the demonstration. The area was searched for leftover fragments, but none were found. Camp Pendleton officials confirmed that an internal investigation had begun to find out why the shell exploded early.
Governor Gavin Newsom criticized the event, calling it an “absurd show of force” and “totally unnecessary.” He said the White House had prioritized publicity over safety. “Firing live rounds over a major highway isn’t strength—it’s reckless,” he said, urging federal authorities to review how the event was approved.
Military officials defended the plan, saying that artillery training at Camp Pendleton was a normal activity and did not usually pose a risk to nearby roads. However, state transportation leaders decided to close the freeway after Friday’s practice firings raised concern. They said event organizers requested signs warning drivers of “overhead fire in progress.”
Tony Coronado, a division chief with the Highway Patrol and a former Marine, said such exercises rarely occur near civilian infrastructure. “It is highly uncommon for any live-fire or explosive training activity to happen over an active freeway,” he explained. “Our first duty is the safety of the public and our officers.”
Matt Rocco, a spokesperson for the state transportation department, said the closure was made “for the safety of the public since live rounds were being fired over the freeway.” The Interstate 5 route is one of the busiest in California, carrying about 80,000 travelers and nearly $94 million in freight every day.
The temporary closure affected both road and rail traffic between San Diego and Los Angeles. Passenger trains running parallel to the freeway were also halted for the afternoon. Local drivers reported delays lasting several hours as authorities cleared the area.
JD Vance, a former Marine and current Vice President, was attending the event with Defense Secretary Pete Hegseth. Both had been invited to watch the amphibious display, which included beach landings and vehicle maneuvers. Vance’s spokesperson later said that Governor Newsom had exaggerated the risks and used the situation for political gain.
Representative Darrell Issa, whose district includes the area near Camp Pendleton, also criticized the governor’s comments, calling the shutdown “a publicity stunt.” However, Newsom defended the state’s actions, saying they were necessary to protect civilians. “We love our Marines,” he wrote on social media, “but next time, the White House should not put people’s lives at risk for a vanity event.”
The Marine Corps said it is fully cooperating with investigators and promised a complete safety review before any future demonstrations.
