SAN DIEGO, CA — A live artillery shell exploded prematurely during a Marine Corps demonstration celebrating the branch’s 250th anniversary, sending shrapnel raining onto a California Highway Patrol (CHP) vehicle and a motorcycle assigned to Republican politician JD Vance’s security detail, according to a CHP report obtained by multiple news outlets.
The incident occurred over a southern California freeway, Interstate 5, one of the region’s busiest transportation corridors. Fragments from the 155mm shell reportedly landed on vehicles parked on an off-ramp, leaving minor dents and scattering debris across the roadway. The premature detonation prompted immediate safety concerns and a temporary shutdown of the highway.
Vance, a former enlisted Marine who served in Iraq, attended the demonstration with Defense Secretary Pete Hegseth at a military base in northern San Diego County. The event included amphibious vehicle displays and live-fire exercises simulating a beach assault. Officials say the exercise was intended as part of the Marine Corps’ 250th anniversary celebrations.
According to CHP officers on the scene, one officer reported hearing what sounded like “pebbles hitting his motorcycle,” while others observed a roughly 2-inch piece of shrapnel striking the hood of a patrol vehicle. Shrapnel was also found along the roadway near the motorcycle, prompting CHP to close a 17-mile stretch of the freeway for several hours. The closure caused significant traffic delays across the corridor, which typically sees more than 80,000 vehicles and nearly $94 million in freight daily. Passenger rail services running parallel to I-5 were also disrupted.
The closure was initially requested by event organizers, who wanted signage posted along the freeway warning of “overhead fire in progress” after practice firings Friday evening. The decision was ultimately made by state transportation officials, who cited public safety concerns.
“This was an unusual and concerning situation,” said Tony Coronado, division chief of the California Highway Patrol. “It is highly uncommon for any live-fire or explosive training activity to occur over an active freeway. As a Marine myself, I have tremendous respect for our military partners, but my foremost responsibility is ensuring the safety of the people of California and the officers who protect them.”
California Governor Gavin Newsom criticized the exercise, calling it an “absurd show of force” and a reckless disregard for public safety. “Firing live rounds over a busy highway isn’t just wrong — it’s dangerous,” Newsom said in a statement. “Using our military to intimidate people you disagree with isn’t strength — it’s reckless, it’s disrespectful, and it’s beneath the office he holds.” On social media, the governor later added: “We love our Marines and owe a debt of gratitude to Camp Pendleton, but next time, the Vice President and the White House shouldn’t be so reckless with people’s lives for their vanity projects.”
Marine Corps officials defended the exercise, stating that live-fire training is routine at Camp Pendleton and that the activity posed no unusual risk. A spokesperson said an investigation is underway, acknowledging the CHP report and the premature shell detonation.
Representatives of Vance pushed back against Newsom’s claims. William Martin, a spokesperson for Vance, told The New York Times: “If Gavin Newsom wants to oppose the training exercises that ensure our Armed Forces are the deadliest and most lethal fighting force in the world, then he can go right ahead.” Meanwhile, U.S. Representative Darrell Issa described Newsom’s objections as a “spiteful publicity stunt” targeting military and federal authorities.
The I-5 closure, combined with the premature shell explosion, disrupted thousands of commuters and freight shipments between San Diego and Los Angeles. State transportation officials emphasized the necessity of the closure to mitigate potential harm from live ordinance fired over the active highway.
In the aftermath, the Marine Corps confirmed that no injuries were reported and that the exercise had been canceled. Camp Pendleton authorities conducted a sweep for shell fragments along the freeway, but none were recovered.
While the Marine Corps maintains that the event followed standard safety protocols, the incident has ignited debate over the appropriateness of conducting live-fire exercises over public highways, particularly in the context of high-profile political visits and anniversary celebrations. Safety officials, lawmakers, and state leadership continue to weigh in, emphasizing that public safety must remain the top priority when military demonstrations intersect with civilian infrastructure.
The event has drawn national attention not only for the unusual circumstances but also for the political overtones surrounding the exercise. As investigations continue, authorities are expected to release further details about the chain of events that led to the premature explosion, the communication between military and state agencies, and measures to prevent similar incidents in the future.