Police are investigating after a sea lion was found beheaded on San Francisco’s Ocean Beach, according to local reports.

Wildlife experts believe the animal was decapitated after it had already died.

“Maybe the person who did this didn’t know that it was illegal, or maybe they did,” Sue Pemberton of the California Academy of Sciences told ABC 7 San Francisco.

She said that sometimes the “legality of it doesn’t really stop people.”

“I don’t really know what this person was thinking, but people might collect them for the novelty of having a trophy of some sort,” she said.

It’s not the first time something like this has happened. Another sea lion was found without its head further down the coast on a beach in Pacific Grove last year, according to SFist.

The individual involved in that incident reportedly tried to carry the head away in a Ziploc bag.

Officials said that interfering with the carcasses of marine mammals is a federal offense carrying serious penalties.

Under the Marine Mammal Protection Act, taking parts from a sea lion carcass is illegal and can be punished with up to $36,000 in fines and a year in prison.

Beachgoers who encounter a dead or stranded marine mammal are urged to leave it alone and report the sighting to local wildlife officials or the Marine Mammal Stranding Network.