i couldn't seize the caravan, they were seriously at the very edge of the map when the mandate was ordered. So far I've 8 dead dwarves (including a grand master engraver, ouch) 6 incarcerated, and 8 hospitalized... only the mayor right now is tantruming, but that's to be expected, he's 13 years old.
Also in the midst of the chaos, I had a dwarf killed by a trap... he was in the captain of the guards squad, but I checked and he hadn't killed or beaten any other dwarves, and he wasn't listed as an enemy of the fortress, so how did that happen?
From what I understand, if a creature falls unconscious on a trap, it will trigger it regardless of how friendly the trap is. Common causes of unconscious states include sleeping, falling 1 z-level (or more, although the impact may prove more explosive thereafter), being caught in Giant Cave Spider webs, and being smashed in the head by blunt force.
It may be prudent to install a large jail if you have a justice system; wooden crossbows are often a favoured choice for the fortress guard as they are not
quite as deadly in beatings but allow the squad to be effective in combat. Failing that, giving the fortress guard a nice, well-appointed barracks with a conveniently lockable door may avert some problems.
"Quickly! Urist McPeasant has exported 2 goose bone teacups!"
"But Sir, the door is locked! We cannot enforce justice!"
"Curses! Foiled by those crafty villains again. Hey, that's a really nice armour stand..."