Err, I know that hit killed the rat, but it kind of killed the wrong rat... >_>
Basically, I was leaving the rat next to the Swordmage alive knowing he'd take care of it, and my risk of moving was meant to put me in position to defend against both rats. If I was just going to kill the rat in F3, I wouldn't have bothered moving and provoking an OA.
It's a little late now, but in the future I would like to stick to my posted actions unless they're incredibly stupid.