Only if we're talking about a single-action revolver with the hammer cocked.
With respect to safety, a Glock is not the same as a double-action revolver that's not cocked.
As has been stated already, striker-fired and SA autopistols in general and Glocks in particular are not the best choice for carry in any fashion that leaves the trigger guard exposed.
An "external" safety can be easily and unintentionally deactivated IWB, and is no panacea compared to a true DAO auto or revolver.
Ultimately, if you IWB or deep conceal, consider a holster or true DAO.
If you have a round in the Glock chamber (which normally gets there by virtue of the slide stripping a round out of the magazine) and rounds in all chambers of a revolver, then pulling the trigger on either firearm will result in a bang. Any belief in “safe action” beyond that point requires too many fairy tale best wishes for my comfort. I have, and use, Glocks, but Mr. Glock isn’t going to be there to comfort my family if I rely too much on his marketing abilities.
Going back to the original story, my guess is that somehow the Glock trigger was pulled.