The elderly black couple
This part of the film baffled the crap out of me. While I can understand possibly calling your neighbor in certain circumstances, I can't see myself calling said neighbor when random people show up at my door in the middle of the night begging for me to call the cops and accusing the neighbor of murder. It just didn't make any sense at all. I may have bought it had the older black guy also called the cops, as well as the neighbor/killer, but not just the neighbor....there's just no logic to that.
Now had they just been trying to get into their house, didn't mention anything about the murders or mentioned them but requested you NOT call the cops...yeah, it would make sense; but not when they are asking nothing of you BUT to call the cops. The bad guys don't generally politely stay where you tell them to, frightened out of their minds, and beg for the cops to be called. That would have made me at least want the cops involved in it before I would even entertain the thought of speaking to the accused neighbor over the phone, much less in person.
It's always better to fart in the toilet than to poop in your pants!