An artillery shell prematurely detonated and rained shrapnel down on California Highway Patrol vehicles during a demonstration at Camp Pendleton that was criticized prior to the event by California Gov. Gavin Newsom, who closed down a highway because of concerns about shells being fired over a busy thoroughfare.

Vice President JD Vance and Defense Secretary Pete Hegseth attended the event honoring the 250th anniversary of the Marine Corps. Newsom lashed out at the Trump administration in the run up to the event, saying "firing live rounds over a busy highway isn’t just wrong – it’s dangerous."

While the Marines had said the demonstration would "comport with established safety protocols" and no roads would be closed, Newsom decided to close a 15-mile stretch of Interstate 5 that bisects Camp Pendleton, the primary connection between coastal San Diego County and Orange County.

During the demonstration, "an artillery round failed to clear the roadway and detonated midflight near Interstate 5 southbound," according to a Highway Patrol report. The round was fired at 1:46 p.m. local time from White's Beach, one of roughly 60 the Marines planned to fire, according to the report.

Metal shrapnel struck a patrol vehicle and motorcycle. An officer described "what sounded like 'pebbles'" falling on his motorcycle, according to the report. Officers found a two-inch piece of shrapnel on the hood of an unoccupied patrol vehicle, which was dented.

The Highway Patrol notified the Marines of the incident and the military ceased firing live rounds. Nobody was injured. Patrol officers swept the highway and determined it was safe to reopen. It was closed from 11 a.m. to 3 p.m. local time.

"This was an unusual and concerning situation," Highway Patrol Border Division Chief Tony Coronado said in a press release. "It is highly uncommon for any live-fire or explosive training activity to occur over an active freeway."

Vance's spokeswoman referred questions to the Marines. Capt. Gregory Dreibelbis with the First Marine Expeditionary Force said "We are aware of the report of a possible airborne detonation of a 155mm artillery round outside the designated impact area."

"The demonstration went through a rigorous safety evaluation, and deliberate layers of redundancy, to ensure the safety of fellow citizens," Dreibelbis said, adding: "An investigation has been initiated. We are committed to determining the incident’s root cause and applying findings to future missions."

Vance watched the demonstration standing atop a 7-ton military truck with his wife. It featured F-18 and F-35 flyovers, parachute landings, Navy SEALs swimming ashore, offshore destroyers and amphibious ships, simulated village explosions and MH-60 helicopters dropping additional SEALs over the water.

The Highway Patrol is recommending an "after-action review into the planning, communication and coordination between federal, state, and local government around the event."

This article originally appeared on USA TODAY: Shrapnel hit California Highway Patrol vehicles during Marine Corps event Vance attended

Reporting by Zac Anderson and Eduardo Cuevas, USA TODAY / USA TODAY

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