March 31 (UPI) -- U.S. Customs and Border Protection said a 61-year-old man died in its custody over the weekend after agents apprehended him for attempting to enter the country from Mexico through a restricted area.
CBP said in a statement Monday that the U.S. citizen died Sunday night at the San Ysidro Port of Entry in California while under its custody.
The man was arrested by CBP agents at the port after he attempted to walk into a restricted area and failed to heed their instructions while also exhibiting "abnormal behavior," the CBP statement said.
San Diego Police Lt. Andra Brown clarified in a statement that the unnamed U.S. citizen had attempted to enter the United States by foot from Mexico through the exit doors of a processing building.
After he was arrested, the man was placed into a cell and a few minutes later CBP officers noticed that he was unresponsive.
"CBP officers with medical first responder training rendered aid until local emergency medical services personnel arrived and took over medical care shortly thereafter," CBP said.
Brown said the man died at the scene.
The San Diego Police Department is investigating and the CBP Office of Professional Responsibility will be reviewing the incident, the federal agency said.