My friend recorded the last episode so I got my hands on it! I've watched the end several times and I've come to the conclusion that AL did shoot Shannon. She said she had one shot left. So when she fired that last shot in the chamber, the slide was still back. Therefore the barrel looks longer and narrow. That's why it doesn't look like a pistol. I even slowed it down frame by frame up to the scene in xjeff99's screencap and it's AL holding the pistol as I described above...just my humble opinion!