It concerns me how specific this is.
Here's the deal. You or someone like you/near you/living with you has murdered a human being. Don't worry. There are simple steps to follow that will ensure your safety.
1. Is it you? Then don't ask this question on a blog read by tens of people.
2. Is it not you? Figure it out quick or you're next, pal.
If it's a family member, who am I to tell you how to deal with it? (Murder them.)
If it's a neighbor, best put your head down and hope that they didn't see you gawking. It also might help to make sure the other people living in your neighborhood are still around. If the killer is just taking out neighbors, as a neighbor, that's something you should probably know.
The stagnancy of the goo is probably relevant. You might have already completely slept through their murderous rage and it might've just been a one-time murder. You're in the clear! However, it could be the stagnancy associated with keeping a person you murdered for a while so you can braid its hair and suck its toes. If that's the case, you're still within the zone of terror for this crazy fucker.
Short Answer: In summary, braid your own hair and remove your toes. Best not to tempt the Neighborhood Neighbor Killer.