PORTLAND, Ore. -- A sea lion was found dead in the Willamette River Tuesday and investigators think it was most likely shot to death.

River patrol found the sea lion and towed it to shore at Kelley Point Park for examination by marine biologists.

Debbie Duffield, a marine biologist from Portland State University leading the necropsy said the sea lion had significant signs of obvious trauma.

“We definitely have evidence that this was human caused,” Duffield said. “At this point, we have fairly good evidence that there was a gunshot wound from a small-caliber gun.”

The biologists also found trauma to the sea lion's shoulder blade, she said, and were able to estimate that the animal had been dead for three to four days. The suspicious sea lion death was also reported to the National Marine Fisheries enforcement division. Investigators said it was most likely killed between Willamette falls and Willamette Park.

Portions of the sea lion will be taken to PSU for a more detailed necropsy and the remaining torso was buried at Kelley Point Park. Duffield said the final necropsy results would likely be released sometime Tuesday.

A sixth-grade biology class from the Caitlin-Gabel school happened to be in the area at the time and helped haul the carcass to shore, then watched part of the necropsy.

(KGW reporter Katherine Cook also contributed to this article.)