Someone is killing sea otters in California, and authorities are offering a big reward for anyone who will turn in the culprit. A total of three California sea otters have been found shot to death near Santa Cruz between Aug. 12 and Aug. 19, according to media reports.

Necropsies later showed that all three of the otters — one male adult and two younger males — had gunshot wounds and died days or possibly weeks ago. Unfortunately, that doesn’t give authorities much to go on, so they will be relying on the public’s help in this case.

Authorities also found a fourth male adult otter that was dead in the area. They suspect a gunshot as well, but are waiting for confirmation.

California sea otters, also known as Southern seat otters, are a threatened species under the Endangered Species Act. Killing one of these creatures is punishable by up to $100,000 in fines as well as jail time. They had been hunted ruthlessly in the 19th century for their pelts, almost to the point of extinction. Fortunately, a few dozen were discovered near Big Sur in the 1930s, and have slowly made a combeack to the point that there are now believed to be about 3,000 otters today.

“Since the 1980s, the species had been recovering in many areas thanks to intensive management and regulatory efforts by several governments,” the IUCN says about the species. “However contemporary issues (oil spills, potential fisheries interactions, predation, and disease events), have either prevented Sea Otter populations from thriving or have caused population declines throughout much of the species range. In the United States, two subspecies of Sea Otters are listed as threatened (E. lutris kenyoni in SW Alaska and E. lutris nereis in California) due to precipitous population declines in Alaska and slow growth (and vulnerability to anthropogenic factors) of a small subpopulation in California.”