Thanks for the replies! I will definitely look into the thundershirts cause we have a lot of thunderstorms in the summer in Calgary. We live in the west part of the city, so we get a lot of stuff rolling in from the mountains. I will see if walking him helps, but I'm afraid he's just going to be confused about why we're not going out. I cannot control him myself as he's too big for me, so I can't take him for walks. He was attacked by a couple big dogs when he was a pup and he's very aggressive with other animals because of it. The vet says he does this from fear, and we haven't been able to re-socialize him because of it.
Thanks again for your help... all replies are appreciated!