Trying to say some dead person, shot by a gunman, might not have had a better chance if he was armed is a joke. It doesn't matter if the room is pitch black you have a better chance to live while someone shooting at you if you also are armed.
No way being unarmed in a theater with a gunman shooting makes you safer then being armed. The gunman shot people after walking right up on them. For sure at that point had the person been armed they would have shot the gunman.
Could people be shot by accident while someone was trying to defend themselvs or others? of course they could that is also 100% reasonable.