I think I was about 12 or 13 at the time, my sister used to have a pair of gerbils, one died, she left home, the other one stayed at home, we used to let it run around the floor in the front room as it liked, it was quite tame. One day I walked in the front room and it came from nowhere darting across the floor and as I put my foot down I accidentelly caught it and stood on its head. I didn't put my actual weight on it or I'd have crushed it like a grape I pulled back realising. But it was enough that it was writhing on its back in agony. I scooped it up in a towel and ran into the kitchen and held it under a tap as blood was pouring out its mouth but it stopped wriggling within moments, dead within about 20 seconds of it happening.

I'd done worse when I was younger still, when 6 or 7, played throw and catch with one of my sisters guinea pigs, where I failed to catch it and it hit the floor more often, it would make a terrifying squeal as it was in air, I left it alone when I noticed it was eventually limping really badly and later on found out it had died and my sister was crying her eyes out. We had this little funeral like thing where the family gathered around and she buried it in the back garden in a pink box which was excruciating. I don't know what posessed me to this day or whether I can use age as an excuse.

When I was around 15 a homing pigeon landed in the garden, it was tired out and lost, gave it something to eat and drink, got a basket with a blanket in, put the pigeon inside it and put the basket inside the garage for the night as it had gone to sleep. Next morning, went in the garage to let it out, the basket and lid was nocked over on the floor, with a decapitated pigeon on the floor next to some entrails with its head. Assumed a must've fox managed to get in through a gap in the garage door, until then I thought animals always killed for food but it had just ripped its head off and left it. I facepalm over this as pigeon trusted me to keep it safe and I didn't realise how important it was to make sure the area was completely secure.