Talk of Lugers always reminds me of this sorry episode.
http://murderpedia.org/female.L/l/longet-claudine.htm
I don't have many ideas for what that would be - maybe an Erma .22? There aren't copies of Lugers that I am aware of, other than that Erma. The whole story sounds fishy to me: guns pointed at people "accidentally" going off is a standard excuse. There are very few people stupid enough to point a weapon at someone and pull the trigger by accident.
An actual Luger-related tragedy occurred back in the 1950s before the Gun Control Act of '68 when people could still buy guns through the mail. Some guy in Texas bought a Luger that was shipped in two parts: the upper and lower halves and the lamebrain that sent it left a round in the chamber. (The victim was also a lamebrain - Lugers show that they are loaded: their extractor is pushed up and the word "Geladen" is visible when there's round in the chamber). The victim apparently removed the wrapping with the barrel pointed at himself and squeezed the sear bar, firing the upper half of the pistol. He died while trying to call for help.