Smith et al. (2008) found that in the very few cases where bear spray didn't prevent injury, it did result in maulings of less severity and shorter duration--it's possible that the bear spray did actually work, but we don't have enough information to know, and we may never have that information. He would have been statistically more likely to be killed or injured worse had he used the gun. A pistol is really unlikely to help.  A .44 magnum can stop a bear if the user is proficient and has time to use it, bear spray is almost twice as effective, statistically, and it can be used much faster and does not require accurate aim. This sounds like a typical defensive/surprise encounter, very unfortunate, and I'm glad Todd is ok.  This highlights the importance of understanding bear behavior and safety precautions, and always being prepared for an encounter. He's a brave and resilient man.