As the humans came to trade, a goblin tried to steal my children. Doors slammed shut behind her as she took her time attacking and killing a dog I had for years. I was not pleased and sent thirty dwarves to beat her to death, as we have no metal and I'm afraid of breaching caverns without any so digging any deeper than my current fort is nerve-wracking. I refuse to give my dwarves wooden weapons and I have nothing to sharpen into stone shortswords but rock salt and it doesn't count as sharpenable, but I digress~.
The goblin panicked and went invisibru mode as my dwarves filed in. She tried to sneak by us and a cage trap suddenly sprung around her. I cackled maniacally, my first prisoner! Oh, what horrors await you, little goblin--
Then I checked my trading post and saw 'Pets' with cages. I frowned. What. I had no pets. Checking up on it, I found that she was now a pet. I ordered her to be moved to the trade depot, cackling more maniacally than before. A SLAVE! A pet! She is mine, mine to sell for lumber so I don't piss off my seven elvish neighbors while I have no metal to defend myself!
...And then the guards stabbed her to death with spears as she was hauled in. No explanation, not even a combat report. Just shank shank deadaedehdded.
I still made a profit selling her junk to them, but what the hell, humans? That was my property and I was going to give you a discount if we worked out yearly trading in slaves, lumber and metal bars!
...Can anyone tell me why they did that, how to keep it from happening again and if this is a rare occurrence, how to maximize my cage trap slave industry? I've thought of trying to sell a slave to the elves, as they have no guards that would murder them on-sight. They just stand there all elfy, awkward and defenseless.