A U.S. Coast Guardsman is dead after a "suspicious" boat rammed his small vessel off the coast of Southern California on Sunday.

Chief Petty Officer Terrell Horne was one of two Coast Guardmen thrown off their cutter's small boat when the suspect's panga-style vessel "suddenly increased speed and maneuvered directly" at them, then struck the boat, Capt. James Jenkins told reporters.

Horne was pronounced dead by emergency medical personnel upon his arrival on shore at Port Hueneme, northwest of Los Angeles. A traumatic head injury was cited as the cause of death.

"Chief Petty Officer Horne was an outstanding Coast Guard member," Jenkins said. "And he gave his life in service, enforcing the laws of this nation.

Jenkins said the crew of a Coast Guard patrol aircraft spotted the panga-style boat near Santa Cruz Island, suspecting "it was engaged in illegal activity.”

While he did not elaborate on the details of the illegal activity, he did describe the boat as a panga -- a work boat often used off the coast of Mexico or Central America that is engine-powered and typically 25 to 45 feet in length.

Pursuing the investigation, the aircraft's crew alerted the captain of the Cutter Halibut, an 87-foot patrol boat, which headed to the scene and noticed the panga "operating with no lights." A small boat was dispatched from the Halibut and headed closer to the suspect vessel, Jenkins explained.

The panga then accelerated and hit the small boat, sending Horne and another Coast Guard member overboard. Two Coast Guard colleagues on the same small boat "quickly" recovered their shipmates, and all four boarded the Halibut as it made its way to the nearest port.

Jenkins said that the other Coast Guardsman tossed overboard was treated and released later Sunday morning from hospital after suffering “relatively minor injuries.”

Reports indicate that while the panga boat made an attempt to flee the scene of the incident, it was later interdicted by a different Coast Guard boat and helicopter. Two people were then detained, the Coast Guard said in a news release, without specifying any charges.

"The Coast Guard, along with its law enforcement partners at the federal, state and local level, are actively working to make sure all of the individuals who are involved with this illegal activity are brought to justice," Jenkins said.