I heard a loud boom that shook the house. At first I thought...

I heard a loud boom that shook the house. At first I thought it was the furnace. I asked my son 'Did you feel that?' It shook the couch. I thought maybe something fell upstairs, or maybe the chimney collapsed or something. I went outside to look around. You can see the town garage from the house; I thought maybe it was the back of the bucket banging. Nobody was at the town garage.