Investigators at Washington state's Department of Fish and Wildlife are trying to unravel an unusual whodunit: Eight sea lions have been found dead in the Puget Sound region, all with bullet wounds. There have been scattered cases of murdered sea lions before, but it's rare to find so many in such close proximity. Here, a brief guide to this troubling mystery:

What happened?
The bodies of seven sea lions were found on the Nisqually River, south of Tacoma, and another washed up on West Seattle's Lincoln Park beach. That animal, a California sea lion, died of a gunshot wound to the lung, a necropsy reportedly revealed. According to the marine animal protection group Seal Sitters, it also had been bitten by a shark, and had twisted intestines, which could have been caused by the bite, fishing lines, or something else. The seven sea lions found on the Nisqually — several of which were also California sea lions — also appeared to have been shot.

It's illegal to shoot sea lions, right?
Yes. California sea lions are protected under the Marine Mammal Protection Act. One of the animals found on the Nisqually was a Steller sea lion, which is protected under the Endangered Species Act. Anyone convicted of killing federally protected animals could face up to seven years in prison, fines, or both.

What motive could anyone possibly have?
Sometimes sea lions are targeted because they are damaging fishing nets or docks. Sea lions on Puget Sound feed on salmon schooled at ship locks leading from the sound into Seattle's Lake Union. A commercial fisherman went on trial this month for allegedly routinely shooting at Steller sea lions when they got close to his nets. Even authorities occasionally try to scare them off with firecrackers and rubber bullets, sometimes capturing or killing those that won't leave. "Unfortunately, some people just don't like the sea lions and seals feeding on fish," Robin Lindsay, an observer for Seal Sitters, tells

Sources: ABC News, Daily Mail, MSNBC, MyNorthwest