I killed a cat.

I want to start by saying I love animals. This is the only time in my life I had ever done something like this. I was about 13 and ran into an old friend of mine I hadn't seen in a couple of years. He was a quazi friend from school and he was always a bit different. So when we were hanging out in one of our backyards we were tossing around a dead mouse (it was already dead I didn't kill it) just having a little fun. He had this giant indoor/outdoor cat that he had never let outside so it didn't know any better. It would just wander around his house and yard. I don't know if it was the way the cat acted or if my friend told me but I just assumed the cat was a stray. So we were tossing the mouse and the cat joined in which made what we were doing that much more amusing. At one point my friend picked me up and tossed me into the corner of a chain link fence. I smashed my shoulder into the fence post really hard and for some reason I don't know I thought this mother fucker cat caused this and I wanted to hurt it. So I stood up and b-lined for the cat. It froze, poor bastard. I grabbed it by its tail, slammed it into the ground. The cat was making these awful noises. I picked it up and bashed it into a tree then I slammed it into the ground again. It went limp so I left it there and walked inside my friends house. I was in his kitchen when his mom came through. She was screaming about her cats at my friend then she asked who I was. She told me to get out and not to come back. I left and spent the next couple of days wondering why I acted like I did or what would be the outcome. I forgot about it feeling it was a complete non issue. Not hearing anything about it I just assumed it had to be ok. Still I never saw the cat again and until now never told anyone. Never the same way but I still get this feeling sometimes.