I had a siege begin and I was hitting them with mortars until I saw that they had all turned on one guy. The raider was dead, but wasn't being killed. He was moving around and melee attacking.
I tried making a save file, but the raider was dead when I loaded up the save. I am not sure how to replicate it.
http://youtu.be/9Xw3HiX36U4
Its a weird bug yeah what I could see is that he was carrying a packaged survival meal x0 somehow (and I dont know how) its glitched and made him invincible. when you reloaded the save file the survial meal got deleted and then he got killed. Thats my nooby explanation :P
I bet that is exactly what is happening. Here is another post that shows the raider with 2 meals
http://imgur.com/a/vDezL
Happened to me also during a siege once! and I remember reading someone else having seen this bug aswell
during a siege one of the pirates decided to pick up survival meal and wander around the map aimlessly
I remember it clearly cause she was acting real shady with that yellow box in her hands and being at the other end of the map
at one point
then getting back to her friends and wandering in daze after most of them were dead (I didn't think nothing of it at this point yet cause it seemed pretty normal)
but then my cleanup crew lodged a lee enfield slug in her head 'killing' her. But she just kept wandering about, only as a corpse this time