I'm a little paranoid by nature (stoked to a rage from time to time by the meth-head feeb living next door), so I'm not going to open the door for anyone I don't know.

Living next door to me (in itself) is not sufficient to place someone in the "someone I know" category. I have a neighbor or two that I do know, and I would open the door for them--but they would probably call or text me if they needed my help.

If you want to know if you did the right thing in not opening the door, IMHO, yes.
You called 911, as you should.