A U.S. man who failed to stop for an inspection while entering the U.S. at the California-Mexico border was shot and killed during a gunbattle with border officers, San Diego police said.

The man was killed at the San Ysidro Port of Entry about 7:45 p.m. Monday and has not been publicly identified, pending notification of his family, but he was described as a 23-year-old white male.

A motive in the shooting was also unclear from the information released Tuesday by San Diego police.

The man, who was driving a white pickup truck, failed to stop for an inspection and drove through the inspection area, according to officials. After being blocked by another vehicle, "the suspect began firing a gun out of his vehicle toward the officers, then exited his vehicle and continued firing at the officers," police said in a statement.

Customs and Border Protection officers returned fire, killing the man, police said. Seven CBP officers were involved, but none were injured.

"It was bullet after bullet after bullet after bullet — it was scary, and we just, I mean, we kind of freaked out," witness Gabriella Berragan told NBC San Diego.

Video captured the sound of gunshots and officials warning people to stay down.

Berragan described the shooting as "terrifying" and told NBC San Diego that she jumped in the back of the car to be with her kids; her boyfriend, baby and 2-year-old daughter were in the car when the shots rang out.

Customs and Border Protection said that San Diego police are the lead investigating agency, but that it would also be conducting a review of the incident.

The San Ysidro Land Port of Entry is the busiest in the Western Hemisphere, with around 70,000 northbound vehicles processed each day, according to the federal General Services Administration's website.