Did any syndromes affect most of your dwarves? Are you playing with diseases on?
I wont do a bugfix for this, because I'm working on the new DF version, which doesnt have that problem anymore, I'm just curious which one was the cause... there is a dfhack script called showunitsyndromes, if you run it on some of the berserk dwarves, it should give you the syndrome name.
Sorry for the loss of your fort.
I think diseases are on. I never turned them off, so if they are on by default then yes. The only reason I know everyone was hostile despite not meticulously picking through the ~3-4 pages of "so and so was interrupted by so and so" and "the stray this or that was struck down" that were generated immediately upon unpausing the game, was that at least a few of the interrupted messages were being caused by babies, indicating that even the babies had gone berserk. I couldn't think of a situation that would cause a baby to kill anything, let alone dogs and cats, in normal df, so that struck me as odd - especially when it seemed like every baby in the fortress was suddenly trying to kill everything. And then I noticed the other dwarves were killing and dying indiscriminately as well.
At least now I know it's possible for a dwarven baby to strangle a cat to death.
As far as the biome is concerned, no it's not evil, but it IS a volcano. The caldera of a volcano in fact. The wildlife is moderately hostile, but nothing too bad. Mostly coyotes and that sort of thing. Sometimes we get raptors, foul blendecs, and xen infectors. I was hoping to build the main entrance drawbridge over the caldera. Might still happen. I've got it set up now so that most everything is inside the fortress. There's only a few things still outside. Ideally it'll be really easy to defend. I've built the military base on a peak that looms over the caldera, so that dwarves stationed there have a good view (through fortifications) of the caldera and thus the future drawbridge. Anything trying to cross can either be shot down on the bridge, or the bridge could be raised to drop the entire invading army into the volcano. Eventually I'm planning on lopping the top off the peak and building a little sun garden with high walls so that dwarves dont get cave-adapted, but can still technically be "inside the fort". If it's on top of the military base, that should prevent it from being too much of a security risk for climbing or flying invaders.
Of course, there's always the possibility the volcano could erupt. That'll be loads of FUN.
Ran showunitsyndromes on a few of the survivors, namely ones who have generated recent reports of wilderness skirmishes. Nothing comes up.