This case reminds me so much of spree killer Andrew Cunanan. Cunanan had a relationship with his first two victims in Chicago. He then went on a cross-country killing spree - killing a man in Chicago and another man, a caretaker at Finn's Point National Cemetery, in Pennsville, NJ. Police believe the NJ man was killed simply so Cunanan could steal his vehicle, which he used to drive to Miami Beach, where he killed Gianni Versace.
I live in South Jersey, two counties from Pennsville, and I remember the fear people had before Cunanan was found in FL after killing Versace. The seemingly random wanderings of a man that could at any moment pop up and kill people - some who had no known connection to him - made it all the more frightening. I don't think a lot of people initially felt vulnerable because the first two victims had a relationship with Cunanan and some LE persons believed there was some tie to the third victim, too. It wasn't until the fourth victim was killed - in the middle of a quiet cemetery in a small, rural town - that people really believed Cunanan was a danger to anyone and became afraid.
PM gives me this same sort of vibe in that he had connections to the first two victims (even though the first victims were only "connected" by being neighbors of someone he was stalking). I fear that he may spiral further out of control and kill people that he seems to see some sort of "connection" to, even if it only exists in his mind.
All of this is IMO and I really hope there are no more victims. And I pray for his victims and their families - including the original girl that seems to have been his target - and for the people of Sandy Hook that have already had to deal with way more tragedy than any place should ever have to deal with.