Mal shoots and kills the poor guy ("Take me with you! Take me with you!") who's about to get eaten by the ravenous Reavers. That man who gets shot is the same one who earlier had tried pulling a gun on Mal and his crew (I hadn't realized that). And what did Zoe say when she disarmed him? "You know what a hero is? Someone who gets other people killed."
She could kind of be describing Mal.
Am I reading too much into that?