SAN DIEGO (AP) — A 40-year-old U.S. citizen died after a border inspector shot him with a stun gun at the nation's busiest crossing, authorities said Thursday.

San Diego police said the man jumped over a counter and attacked an inspector after being taken to a separate area for questioning at the San Ysidro port of entry connecting San Diego and Tijuana, Mexico. A records check showed he was wanted on a felony charge.

In a statement, the U.S. Customs and Border Protection agency said the man attacked two inspectors, and it described him as "combative." It said officers found heroin during a body search.

The man attempted to enter the U.S. on foot Wednesday afternoon, according to the agency.

Authorities attempted to resuscitate the man, who was pronounced dead at a hospital.

Police said the man would not be identified until his family was notified.

Four customs officers suffered injuries and were hospitalized. Police called the injuries moderate; the agency said they were minor.

About 50,000 motorists and 25,000 pedestrians enter the country daily at San Ysidro.