you run along with some sailors to the main deck. as you enter it you see several of the sailors there aiming crossbows at the front, where a sailor holds one of his hands over the other, trying to stop a bleeding. at first you dont notice it, but you realize that the prisoner is standing right behind the man. he whispers something to the sailor before he leaves his own knife in his back and jump into the water.
the other sailors rush forward to help their comrade the same second he is stabbed, pushing you away to get to him.