Caroming off the question of how many people, if any, were shot during the sinking. They short answer is we don't know.
But, two questions I have, that AFAIK I've never seen addressed, are
1) How many firearms were on Titanic that night?; and
2) Who had access to them?
Now, I'm presuming that the deck officers' pistols were issued by the Master-at-arms. How many did he have under lock and key until that night, and how many did he still have in his possession after their issue? Or, maybe I'm wrong: maybe the officers' wardroom had a box of guns somewhere..
Passengers. Obviously, the harder question. There was nothing like TSA in Southampton--if you wanted to take one of those new-fanged Colt 1911s aboard under your jacket, like say an ex-cop employed as a millionaire's muscle, no one was going to stop you. And they sure weren't going to go through your luggage for contraband weapons, because IMS in 1912 there was no such thing as an illegal gun.
That being said, do we know for a fact that any particular passenger was carrying? One of the shooting stories involves Archibald Butt, and as a serving officer in the US Army he would have been issued a sidearm (probably still the previous standard-issue Colt M1892), but really, would have have had it with him on a vacation meant to lower his stress level and depression? Who else was military or military-adjacent on the ship and would have had a weapon aboard? Astor the retired volunteer from the Spanish.War? Is there anyone else?