​Man dies after being shot with stun gun at U.S.-Mexico border

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

San Diego police said the man attempted to enter the U.S. on foot Wednesday afternoon at the San Ysidro port of entry connecting San Diego and Tijuana, Mexico. He was held in a separate area for questioning where a records check showed he was wanted on a felony charge.

"As agents attempted to take the male into custody, he jumped over the processing counter and attacked an agent, San Diego Police Lt. Paul Rorrison said, according to CBS affiliate KFMB in San Diego.

"The male would not comply with the agents' instructions and had concealed his hands from the view of the agents. One agent used his Taser in an attempt to stop the male's combative behavior," Rorrison said. "The male became unresponsive and stopped breathing."

The U.S. Customs and Border Protection agency said in a statement that officers found heroin during a body search.

Authorities attempted CPR on the man, who was pronounced dead at a hospital. A medical examiner will determine the cause of death.

Police said the man's name would not be released until his family was notified.

Four Customs and Border Protection officers suffered injuries and were hospitalized. Police called the injuries moderate; Customs and Border Protection said they were minor.

Customs and Border Protection said San Diego police, the U.S. Department of Homeland Security's inspector general and its own internal affairs office would investigate.

About 50,000 motorists and 25,000 pedestrians enter the country daily at San Ysidro, more people than the top two U.S. airports for international arrivals combined -- New York's John F. Kennedy and Miami.