When I was 7 or 8 I had a hamster, and for whatever reason, I put it in a little purse to carry it around...started running and the purse smacked into a door. Hamster I believe died from a concussion in about 5 minutes...I was traumatized from that for a long time, but I definitely learned from it and I was always a lot more serious about handling my future hamsters and small animals.
I recently caused the death of a kitten a couple of years ago. It was a feral kitten that somehow got left by the mother at my boyfriend's house. She was at the backdoor and she got under my feet and I stepped on her and broke her leg. We took her to the vet but we were told she was too small to have it set. They said they could amputate, but they estimated $3000 total and we couldn't possibly afford it and take proper care of our other pets. We opted to have her euthanized. :( Poor baby...I felt so horrible. I still feel horrible about it...
These deaths weren't caused by me, but the feral cat population used to be really rough in my boyfriend's neighborhood. He lives with his elderly grandparents to help them out, and they eventually got several of the cats taken to a reserve for feral cats where they spay/neuter them and release them into the reserve, and that really helped. But we used to find litters of kittens that were sick or hurt all the time. We found two that had been laid in a bed of red ants and the flies/ants had just eaten them up - they were hurting and crying and my heart was just broken. It was a Sunday and the vet was closed, and we called my boyfriend's uncle to shoot them. It was the kindest thing we could do, because they were suffering so much. We found another kitten that was sick from god knows what - she was only a couple of weeks old, so tiny. She was hurting so bad that she would just scream if you even touched her. It was also on the weekend and the vet was closed, and she was so close to dying we opted to shoot her too to end her suffering.
I ran over one with my car one day too. It was under my tire and I didn't see it, and I backed out, didn't look back at the spot, came back, and realized what I'd done. That one upset me pretty bad...I check under my car always now.
Boyfriend did save a puppy that someone ran over and didn't stop to help. It was the middle of the night and it was hurt pretty bad and had a collar with no tags, so he called the police and they sent someone from the humane society or something and they got it some vet care I understand...not sure if he made it, but being euthanized is better than dying in the road or being hit again!
Cinnamon Whiskey 11 y/o 15hh Chestnut AQHA mare, 2'6 Jumpers