A passer-by made an emergency call shortly before 11:30 a.m. to report seeing the possibly armed man next to a car and a recreational vehicle pulled over on the shoulder of northbound lanes, near state Route 52 in National City, according to the California Highway Patrol.
Officers halted all northbound traffic in the area and detained four people at gunpoint.
All lanes were reopened within about 15 minutes.
No arrests have been made.
