Authorities discovered a deceased man after intercepting a small boat carrying illegal migrants 14 miles west of San Clemente Island on Wednesday. Coast Guard and Customs and Border Protection officials found 21 individuals aboard the vessel, including the unresponsive 56-year-old man.

Upon boarding the craft, responders initiated CPR on the man before a military helicopter was dispatched to evacuate him for medical treatment. A Coast Guard Air Station Ventura MH-60 Jayhawk helicopter crew conducted the medevac, continuing CPR during the flight to Ronald Reagan UCLA Medical Center in Los Angeles. Hospital staff were able to restore the man’s pulse, but he ultimately succumbed to his condition.

The identities of those aboard the boat, including the deceased man, remained unknown. Officials reported the boat’s presence following a tip from a bystander who reported a suspected alien smuggling vessel near San Clemente Island, but the origin point of the vessel was not determined.

The remaining 20 migrants were detained and transferred to U.S. Border Patrol custody. San Clemente Island, part of California’s Channel Islands, is situated approximately 78 miles west of San Diego.

Coast Guard images showed a small, crowded vessel with several occupants wearing life jackets. Authorities continue to investigate the circumstances surrounding the interception and the man’s death.