A friend of mine and everyone else in the Gettysburg area had some unneeded excitement about 3 AM. He was working in his church and felt the whole building shake and heard a loud 'thump'. He actually thought someone had driven into the building, and then went outside and saw that everyone else had experienced the same thing. He said it sounded like someone set off a massive load of ordnance south of the town to rattle everything for a few miles around.

He says the local cops are looking into it, and the current opinion is they they had a large bolide blow above the town.

I have read elsewhere of similar loud booms happening in various parts of PA since last year, so who knows?