Lost another one. 30 some odd dwarves dead because of a stray right hand.
See, my rangers had just dropped a hostile Giant Crow Zombie out of the sky. As a safety measure I had a refuse pit behind a number of doors and an experimental hatch & pressure plate system. Worked half the time, needs some refining. Had a pretty decent pile of zombies in there, as well as a few unlucky dwarves and their ghosts. Anyway, as my ranger was bringing his recent kill to the dump point, it sprung to life. He killed it quick enough, so I thought all was well and went on my business.
I never even noticed that the Crow snapped off my rangers right hand. There was no blood and he just went on with his business. I had also went on with my business, further digging out my meager holdings. It was a short while later that I received a few notices of Urist McFarmer has been missing for a week, Urist McJewler has been missing for a week, etc, etc. And then I noticed the zombie outbreak that was quickly growing. No military to stop it and knowing my end was near, I decided to check the combat logs and figure out what the hell just happened.
One lucky strike by the severed right hand of the Ranger. Managed to hit a farmer chucking some refuse in the head, pushing his skull into his brain. And so, patient zero went on to infect the rest of the food production sector.