Burying beetle

the wiki doesn't do this creature justice.... this is a carrion beetle. It buries whole carcasses, usually of rodents or birds and then lays eggs in the chamber it creates. Pairs of beetles usually take 8 hours to completely bury and strip the dead animal of it's fur or feathers. Not only that... they secrete chemicals that are anti-fungal and anti-microbial to keep their food from rotting prematurely... groups of beetles can cooperate to bury larger animals and will raise their young communally.

There are several that are difficult to differentiate, but I found a list of species that appear in Washington state, which helped narrow it down, so I think this is likely correct.