Marines Issue Findings on California Shrapnel Incident

The October episode sent shrapnel onto California Highway Patrol vehicles on Interstate 5 during a celebratory exercise conducted for Vice President JD Vance and Defense Secretary Pete Hegseth.

A “one-in-a-million” malfunction caused an artillery shell to explode prematurely over Interstate 5 in California during a live-fire weapons demonstration for Vice President JD Vance and Defense Secretary Pete Hegseth in October, a Marine Corps general concluded in an investigatory report released on Friday.

The explosion sent shrapnel flying onto a California Highway Patrol vehicle and motorcycle that were parked on the freeway as part of Mr. Vance’s protective detail, bringing the exercise to a halt.

Nobody was hurt, but the episode resulted in verbal fallout because Gov. Gavin Newsom of California, a Democrat, and the Trump administration had been feuding over whether the military display was safe and traffic should have been allowed to flow as munitions were fired.

The Marines faulted the projectile’s fuze, a device screwed into the nose of an artillery shell that initiates an explosion. During the demonstration, on Oct. 18, Marines used an electronic time fuze that was certified as safe to fire over the heads of troops in combat and was “manufactured to a one-in-a-million defect standard.”

It was unclear why the fuze had malfunctioned, though the report said the error could have been caused by the “near simultaneous” firing of two large artillery weapons called howitzers, using powerful propellant charges, that were positioned close to one another. The report also noted that there was the “potential presence of anomalous electromagnetic energy” that could have interfered with the timing of the detonation.

The Marines’ investigation noted there had been only one previous incident with the same fuze that was used in October, during a 2017 live-fire exercise in Fort Drum, N.Y. In that episode, the report said, the premature explosion of the shell was likely caused by the projectile hitting a bird midair.

The report determined, however, that it was improbable that the shell had struck a bird in flight at Camp Pendleton, outside San Diego. It also found that the guns’ alignment precluded the possibility that two shells collided midair.

The Marines concluded that military personnel were not to blame.

The demonstration for senior federal officials was arranged as a celebration for the 250th anniversary of the Marine Corps, which was founded on Nov. 10, 1775. It involved Marines landing from the Pacific Ocean on a training area called Red Beach, just west of I-5 — a main north-south artery in California.

Days before the celebration, a dispute erupted between the White House and Mr. Newsom over whether the heavily traveled freeway should be closed during the demonstration. State officials wanted to close the road to the public for safety reasons, but federal officials said it was safe for it to remain open.

The day before the event with Mr. Vance and Mr. Hegseth, the Marine Corps set up M777 155-millimeter howitzers on the beach and conducted a practice run by firing 30 rounds over Interstate 5 as traffic flowed, without incident, the report said. The shells landed on a training area on Camp Pendleton.

On the day of the event, Mr. Newsom ordered a 17-mile stretch of the freeway closed hours before the start time, causing significant traffic delays in Southern California. The closures drew condemnation from the White House and conservatives, who accused the governor of unnecessarily trying to generate motorist ire toward the Trump administration.

The report states that President Trump was originally scheduled to attend the Red Beach demonstration, and that the U.S. Secret Service would have required the closure of Interstate 5 because the freeway had “multiple line-of-sight locations along the I-5 corridor” and was too close to the intended viewing platform for the president.

However, the document indicated that on the same day the White House decided to send Mr. Vance in the president’s place, it was determined that the interstate “now has the possibility of being open to traffic.”

After the event, Mr. Vance, who served as a Marine public affairs specialist in Iraq, called the display of firepower “a “testament to the Corps’ strength and unbeatable power.”

The Marines’ report said that six howitzers were on Red Beach for the demonstration, and they had 120 high-explosive shells available for use. During the howitzers’ first volley, one shell exploded over the highway and the order was given to “check fire,” which temporarily halted the event.

That shell exploded at an altitude of 1,529 feet, according to the report, and more than half a mile away from where it was launched.

After the release of the Marine Corps’ investigation, Mr. Newsom’s office still described the incident as unnecessarily dangerous.

“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,” Izzy Gardon, a spokesman for Mr. Newsom, said on Friday.

A spokesman for Mr. Vance did not immediately respond to a request for comment.

According to the report, the six howitzers were placed in an area roughly 165 yards long by 165 yards wide. Two of the guns were just 14 feet apart from each other.

“Several career artillery officers note they have never seen howitzers placed this close together,” the report said, while acknowledging that there is no minimum distance between howitzers that is required for training missions.

Malfunctions took two of the howitzers out of action, leaving only four guns, which each fired a single shell on Oct. 18.

The fuze used on all of the artillery shells fired that day were M767A1 electronic time fuzes, which were designed to explode after a certain amount of time that is calculated and inputted by artillery gun crews before firing. Each fuze has a secondary feature that should cause it to explode on impact with its target.

The lot number for the fuzes used that day indicate that they were made by BT Fuze Products, a division of L-3 Communications, in December 2004. The manufacturer, now known as L3 Harris, was not immediately available for comment on Friday.

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