A Gun? In the Krav Maga book on Weapon attacks it goes into detail about how long it takes to un-holster a gun, aim and fire it. Unless you are walking around with it pointed, it probably will be of no use in a surprise attack. A scary idea at best, and there are too many records of weapons being used against their owners for my comfort. Mace might be a better choice. Krav Maga specifically states that it is good for the elderly and children. In the right atmosphere of training, I agree.
Old people can move very fast when motivated. A friend of mine is a sharif and shared this story with me. One of his co-workers arrested a guy that tried to rob an old lady. She counter attached with such furious movements that she overwhelmed him. When the officer showed up the assailant was begging to be arrested. They had to restrain the lady as she was crushing his chest with stomping blows. The best part was when they put him in the jail cell with a bunch of tough guys; they asked what he was arrested for and the officer told them, in detail. *lol*
Regarding the book. My son was doing a report on sports injuries for school, and I picked up one of the books he had requested from the San Diego County library. I believe it was the Sports Medicine Bible by Micheli Lyle J. But, I am sorry, I can’t guarantee this source.