Countless, indeed  because the NRA suppresses research.  Seems like if the gun industry knew seniors (or any other group) were safer with guns than without, they wouldn't suppress research.  You'd rather go with anecdotal evidence, except when you choose to ignore inconvenient anecdotes, like you are ignoring mine.
Everyone gets old and dies.  Everyone.  Some get dementia, some don't.  Some people go crazy when they are young.  
I was upset (as were many) when this poor man, in my home town, shot his wife.  I was suggesting how it could have been prevented, as the title of the article I am commenting on said. 
Your point is let crazy people keep their guns, they don't always shoot their domestic partners, maybe not even often.  And your additional point is when a woman is shot in the head but despite all odds, with much hard work learns to walk and talk again, and she and her husband who own and shoot guns, work to add a wait time before buying a gun, they are evil.
Wow.