An environmentalist who worked to protect leatherback turtles on Costa Rica's Caribbean coast was found dead Friday on a beach used by drug traffickers, authorities said.

Costa Rica's Judicial Investigation Police said in a statement that a motive in the killing of Jairo Mora Sandoval has not been determined.

Mora Sandoval was a volunteer with the nonprofit group Widecast, which protects turtle nests from poachers in Moin beach in Limon province.

His beaten body was found Friday. He had had his hands tied behind his back and had been shot in the head, said Widecast director Didiher Chacon.

Mora Sandoval, 26, had been patrolling the beach along with four other female volunteers Thursday night when masked men kidnapped them. The women escaped their attackers and went to police, Chacon said.

Chacon said he suspects drug traffickers are behind the killing. He said Moin beach is used to bring in drugs.

"There are several drug dealers who are known to authorities and who need the beach totally deserted," Chacon said.

Chacon said he has decided to remove all of his volunteers from Moin, leaving the turtle eggs exposed to poachers, who sell each egg for $1.

In a message posted on its Facebook page, The U.S. Embassy in Costa Rica called Mora Sandoval's killing "senseless."

Mora Sandoval was "a committed Costa Rican environmentalist who was sounding the alarms about threats received from anti-wildlife criminal groups and drug traffickers," it said.