SAN LUIS OBISPO, Calif.—Three elephant seals were found shot to death Saturday at a breeding ground along the central California coast, authorities said.

Docents with Friends of the Elephant Seal found the dead mammals covered in blood at about 9 a.m. near the public viewing area of the Piedras Blancas rookery, about 12 miles north of Cambria.

The shooting likely took place sometime after 4:30 p.m. Friday, officials said. Park Ranger Leander Tamoria said the shots likely were fired from the top of the bluff, perhaps from the public parking area.

"These animals are essentially defenseless. They sleep and rest at this place. They wouldn't have been a threat," said Special Agent Roy Torres of the National Oceanic and Atmospheric Administration, which is leading the investigation. Torres called the crime "just brutal in nature."

State park rangers and wardens with the state Fish and Game Department are assisting in the investigation of the killings, which took place on state park land.

Two of the dead animals were about 3 years old and weighed up to 1,000 pounds apiece, officials said. The third was approximately 2 years old and weighed about 600 pounds.

State park officials are offering a reward of up to $5,000 for information leading to the arrest of those responsible.

Northern elephant seals are protected under the Marine Mammal Protection Act. Disturbing the animals is a federal offense; injuring or killing one can be prosecuted as a misdemeanor resulting in penalties of up to $12,000 and criminal fines of up to $20,000 and imprisonment.