A “one in a million” fuze malfunction caused a live Marine artillery shell to explode prematurely over Interstate 5 near Camp Pendleton last October, raining shrapnel onto California Highway Patrol (CHP) vehicles and reigniting tensions between state and federal officials. The findings come from a 666-page Marine Corps investigation dated December 19 and released publicly last week.
The shell exploded during a celebration of the 250th anniversary of the Marine Corps on October 18, at Marine Corps Base Camp Pendleton, north of San Diego. The event was attended by Vice President JD Vance and Defense Secretary Pete Hegseth. Nobody was hurt.
According to KPBS, the investigation found that a faulty electronic fuze caused an M795 high explosive round to detonate early, at an altitude of roughly 1,480 feet, shortly after launch at 1:46 p.m. The round was fired from an M777 howitzer positioned on a beach west of the freeway. The shell was part of a planned 60-round demonstration that was immediately halted after the malfunction.
The report concluded there “is no definitive answer” as to why the round failed, noting the fuze “is manufactured to a tolerance of one defect in a million.” Investigators ruled out any negligence or wrongdoing by the Marines involved. They also ruled out bird strikes or mid-air collisions with other shells.
The explosion scattered shrapnel onto the freeway, striking a CHP motorcycle and an unoccupied Ford patrol car — both part of Vance’s motorcade. An officer reported hearing what sounded like “pebbles” hitting his motorcycle. A two-inch-by-half-inch piece of metal left a small dent on the hood of the patrol car. CHP sergeants swept the highway lanes and found no other metal fragments. Both directions of I-5 reopened about 30 minutes later.
Investigators pointed to two possible contributing factors: the six howitzers being arranged unusually close together — in a roughly 35-meter stretch on Red Beach — and the “potential presence of anomalous electromagnetic energy in the vicinity.” Base range control officials told investigators that artillery hadn’t been fired from that beach since the late 1950s, and until the rehearsal on October 17, had never been fired over traffic on I-5.
Doug Krugman, a retired Marine lieutenant colonel who led infantry units in Iraq and Afghanistan, said the arrangement of weapons was tactically unsound. “In modern warfare, putting six artillery pieces in a … 35-meter-long stretch on a beach … would be tactically extremely unsound and a horrible idea,” he told KPBS. Krugman also said the demonstration served mainly as a photo opportunity for the Trump administration, adding, “The weapons were packed that close together and they were shooting from that beach to make sure it was a good photo opportunity.”
Emails included in the investigation reveal the celebratory tone surrounding the event. “It will be a good show regardless of who shows up,” Marine Corps Commandant Gen. Eric Smith wrote in an October 14 email to Brig. Gen. Garrett “Rainman” Hoffman of the White House Military Office. President Trump ultimately did not attend.
The freeway closure itself became a flashpoint. The day before the demonstration, California Gov. Gavin Newsom — who had called the exercise dangerous and unnecessary — ordered a 17-mile stretch of I-5 shut down after practice rounds were fired across live traffic during Friday’s rehearsal. That decision drew sharp criticism from the White House and congressional Republicans, even as the Marine Corps maintained the exercises wouldn’t endanger motorists.
A December 5 statement from a Marine — whose name was redacted in the report — noted that the Secret Service had wanted I-5 closed due to security concerns for a “Very Very Important Person” — a reference to President Trump — because of the freeway’s proximity to the demonstration’s viewing area.
After the malfunction, 26 California House members and the state’s two senators sent a letter to Hegseth demanding answers about who authorized live fire over the freeway and what safety precautions had been taken.
Newsom’s office pushed back forcefully on Thursday (March 19). Diana Crofts-Pelayo, a spokesperson for the governor, said in an email, “We’re thankful to the Marines for their thorough and precise investigation — in stark contrast to the dangerous and performative demands by JD Vance and Pete Hegseth to shoot live ammunition over a civilian area for their entertainment.”
As reported by Military.com, multiple people interviewed for the investigation said they wouldn’t have changed anything about the event, noting that the Friday rehearsal went smoothly and that safety checks were performed more thoroughly than usual. The investigation did not identify any recommended disciplinary actions.
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