JD Vance

What began as a grand salute to the U.S. Marine Corps’ 250th birthday in Southern California turned unsettling when artillery shrapnel struck vehicles traveling along Interstate 5 — one of the state’s busiest highways.

The incident occurred Saturday during a large-scale military demonstration attended by Vice President JD Vance. The California Highway Patrol said a round fired from a towed howitzer “detonated prematurely overhead,” scattering fragments that hit at least two vehicles — both part of Vance’s protective detail. No injuries were reported, though officials described the situation as “unusual and concerning.”

The celebration, billed as the largest Marine demonstration …