Our dog tried to eat his way into the house, i want it put down or to let it go?

Well I live in a small house w/ my gf and we a small yard. recently we had two dogs but the younger one died and the older one stayed alone. anyway we went out of town and when we got back we found the dog in the house, he had eaten up the back door frame and broken into the house and eaten up the furnitire. well when i saw him i grabbed my shotgun and was going to shoot him b/c i cant afford to fix all that or get it training but my gf tackled me and made me put it up. its a dog my gf has had since she was 11 (shes now 19 im 20) and she loves it but i want it dead. she said she will break up w/ me if i get it put down so my plan right now is to get up early in the morning and let it out into the road before night. my gf would fall for it bc our backdoor is still broken so the dog cld get out into the road. am i bad for doing this ? that dog destroyed our house