They were questers for a goblin who, I think, belong to a human civ. The questers themselves were a mixed bunch of humans, goblins, and elves (there aren't many dorfs in the world), and I don't think I've seen any dorf visitors (not counting the necro and some of his undead minions).
The end(?) result is 4 dead citizens (one kid, one elven mayor, and elven woodcutter, and on founding dwarf [and one of the 3 mothers in the fortress, but the next generation is coming along]), a number of animals, and 70(?) or so infiltrators, with 8 locked up and remaining to be dealt with. A working strategy seems to be to attack those raging (at least possible to spot) and then those who are not panicking (with a preference for those fighting, but there's no way to see those really). A lot of injuries, of course, so we'll see if there are more casualties. Down to 46 citizens.
I had to mop up 4 infiltrators I'd locked into my corpse disposal facilities, as I need somewhere to dispose of all those corpses (and parts thereof).
I'm going to replay this (I saved just a few days before the mess broke out) so I at least react immediately, rather than days later (e.g. sending the training squads out to live action rather than barracks training), as well as making more use of the paltry containment measures I have.
Edit:
I managed to wrangle around until DF didn't crash (I've written a bug report) and ended up with not getting into a fight at all (the skulker fled). However, half a year later or so, a 120 strong army of warriors was announced. Since I didn't want a repeat, I closed off all entrances, with the intention to let the buggers get themselves killed by the next goblin siege. However, they stopped pouring in instead, so only 30 or so entered the map. When I opened up in spring (to allow for an elven caravan) they didn't continue to pour in, but new "real" visitors were announced.
After having stripped the second latest goblin siege of their items, I still hadn't gotten everything, and my citizens started to go to the map edge to take invisible things, as if I'd stripped a bugged merchant caravan of things. As I haven't done that, I suspect the dorfs are stripping former quester visitors of items designated for dumping, which I'd done shortly after the first infiltrator attack (only 7 or so infiltrators) many years back, so I think isolating the fortress while the army was inbound cased the ones who hadn't entered to be stuck in limbo, but I haven't investigated that further, so I don't have enough for a bug report.