In the winter? In Minnesota?
Clearly you're letting logic interfere with what could be an enjoyable mass of unsupported assumptions.
Doctor: Slain Teen Was Intoxicated On Cough Syrup
A purple drank guzzling hottie and her boy roaming the countryside looking to make something happen.
Unfortunately for them they went back to the well one too many times.
The old man was scared because the bastards were back again.
Perhaps he's a freaking loon that's for doctors to argue about. The long and short of it is though, these two dead punks brought this on to themselves. It's not like the old man went out looking for them.