The incident took place at approximately 1:46 p.m. near White’s Beach, roughly three-quarters of a mile south of Las Pulgas Road, while the freeway closure was in effect. According to the CHP report, an officer said he heard what sounded like “pebbles” striking his motorcycle, and another officer observed a roughly two-inch piece of shrapnel dent the hood of a patrol vehicle. Following the mishap, firing of the remaining howitzer rounds - planned as part of a roughly 60-round volley - was cancelled, the freeway sweep found no additional fragments, and the highway reopened at around 2:20pm.
The demonstration - attended by Vice President J. D. Vance and Defense Secretary Pete Hegseth - took place on the beachfront training area of Camp Pendleton. The choice to fire live artillery over a major transportation corridor triggered sharp criticism from California Governor Gavin Newsom, who had warned against the move and ordered a 17-mile stretch of I-5 closed ahead of the event, citing public safety concerns.
“It is highly uncommon for any live-fire or explosive training activity to occur over an active freeway,” CHP Border Division Chief Tony Coronado said in a statement.
The Marine Corps confirmed in a brief statement that it was “aware of the report of a possible airborne detonation of a 155 mm artillery round outside the designated impact area … an investigation has been initiated.”
Governor Newsom took to social media to lambaste what he called a “reckless” demonstration and stated that while California “loves our Marines,” the decision to fire live ordnance over a major freeway was unacceptable.
From the Vice President’s side, spokespersons defended the demonstration, stating the exercise had met safety protocols and suggesting the governor’s objections were politically motivated.
Live-fire artillery exercises are routine at Camp Pendleton in certain ranges; however, firing across or over major public infrastructure such as I-5 is rare and generally considered high risk. Multiple sources familiar with Marine Corps artillery training told press that such exercises normally occur on approved ranges east of the interstate - not in proximity to active freeway traffic.
The controversy highlights friction between federal military planners and state transportation/public safety officials. Ahead of the event, Newsom argued the demonstration was more about optics than training, calling it “a profoundly absurd show of force that could put Californians directly in harm’s way.”
Though no injuries have been publicly reported, the incident raises key questions about coordination between the Marine Corps, the California Highway Patrol, the California Department of Transportation (Caltrans) and local emergency services. The highway closure, lasting hours, impacted daily commuters and freight transport along the busy I-5 corridor — a key artery that carries tens of thousands of travelers and millions of dollars in freight daily.
Investigations underway will likely focus on the artillery shell’s fuze mechanism (which some experts say is the likely cause of a premature detonation), the trajectory used relative to the freeway, communication protocols about the closure, and whether the exercise should have taken place over a major traffic artery.
Originally published on October 19, 2025.