My family spent vacation time each summer camped in a trailer on a "permanent" lot at a campground in Newaygo. The park was called "Sandy Beach," even though their really wasn't much of a beach or much sand on it.
I've always preferred the company of myself to that of a bunch of other people, so I'd spend much of my time just wandering around finding my own little imaginary adventures. One particular day I was at the south end of the park, where there was a largely unpopulated area I liked to fart around in. I was just skipping stones and hanging out. A number of ducks had gathered nearby. It looked like a family of ducks, maybe a mom and two young children. I noticed the ducklings would see the rocks splash and swim toward the resulting circles in the water. They must've thought it was food. This was a fun game of duck teasing.
It was fun until I threw a rock a little too far and hit one of the younger ducklings in the head, snapping its neck. The poor thing was swimming around frantically trying to hold its head above water, but couldn't. I ran out into the river and grabbed it, trying to hold its head up and help it swim, royally pissing off its mom. It wasn't working anyway, and eventually I gave up. Not long after that the little duck drowned right in front of me and its family. I cried out that I was sorry and just sat down in the sand and sobbed. A long time passed, and the duck's mother also finally gave up and swam away with her remaining child. Pretty sure that was the last time I ever deliberately teased any animal for any reason.