The police blotter says the skulls appeared to be freshly skinned. Ten were on the lawn and two were on the porch, one in a chair.
The two residents said they had no idea what the skulls were doing on their lawn, but one said he had run off some neighborhood kids the previous night and they may be responsible.
The skulls were thrown away in a trash bin. The police report doesn't identify the animals, but in photos posted on Reddit they appear to be butchered sheep.
The troll is a statue under a bridge in the Fremont neighborhood.