Five dead sea lions have washed ashore in West Seattle, including four that died of gunshot wounds, according to NOAA.

SEATTLE — Since September, six sea lions have died from gunshot wounds in central Puget Sound and Kitsap County.

The Seattle Times reports that another seven are suspected to have died from "acute trauma" caused by humans, including a decomposed sea lion with its head sliced off found washed ashore Tuesday in a West Seattle cove.

That's according to Seal Sitters Marine Mammal Stranding Network, a group that responds to reports of stranded or dead sea lions.

Michael Milstein, a NOAA Fisheries spokesman, has confirmed the deaths of five California sea lions in West Seattle, including four that died of gunshot wounds.

NOAA Fisheries law-enforcement agents are investigating these crimes, which are prohibited under the Marine Mammal Protection Act.

A $5,500 reward has been offered for information leading to the arrest and conviction of the people responsible for shooting the sea lions that washed ashore near West Seattle.