Initially, I wondered if the heavy rains that occurred in that area over several months could have unearthed some old graves in cemeteries and an animal dispersed the remains. But I don't know of any cemeteries in that immediate area. There is one up on 22nd Ave but that's too far away. And anyway, what kind of animal would be big enough to drag or pick up the decomposed remains of a human head. Only a big dog, a really big dog, IMO, and that's a stretch.
I went to the Dollar Tree on 34st the last time I was in the area (I live in Ontario) and there were quite a few people who appeared homeless to me hanging around the store. A man was lying on the ground outside and people just walked around him. One woman called the cops. He appeared to be very sleepy rather than ODing. The woman at the cash actually locked the door to the store to stop people coming in and stealing stuff right under her nose while she was checking people's purchases out. So there is a bit of drama in the area.
If the head was attached to a body recently it couldn't be too far away. I wonder if there are any vacant homes around where a homeless person could have expired. It's quite a mystery.