Trowa ran through his options. That voice had been... reminiscent of Lady Une during the war, and therefore, if he shot her and she survived it would not make his life any easier. However, she was wearing what did not appear to be part of her body, or if it was, seemed to be more like a turtle's shell than anything else.
Trowa could be very, very precise when he wished it.
Bullets smashed into the armor on either side of her shoulders, hopefully loosening her grip enough for the old man to break loose and flee.