An ethical question for you

Sorry for the blog silence today, but I've been working on deadline and, 13 hours into my work day, I'm still working. However, I thought I'd take a break and pose an ethical question for you all. I'm genuinely seeking an answer here. I just learned that one of my Mom's elderly friends, who last took a driver's test about two years ago, is blind in one eye and has a significant cataract in the other eye. He's also a self-described bipolar personality, who suffers severe, uncontrollable rages. My question is, should I notify the Motor Vehicle Department that issued him the license? There are a few wrinkles that need to be considered: 1. All my information about his condition is second or third hand (meaning that it comes first from my mother, and may come to her through the man's wife). 2. If I notify the DMV, even if I do it anonymously, he'll almost certainly figure out that the information originated with my mother, potentially destroying a friendship. 3. I have no information that he's had any accidents in the past. Frankly, if my mother's information is correct -- and she's pretty reliable at ferreting out and retaining information -- I find it very disturbing that he's still driving. I recognize his need for independence, but it's very selfish (and quite possibly unethical) of him to put not only himself at risk -- after all, he's free to make that decision) -- but everyone else on the road at risk too. On the other hand, it's rotten to be a busybody; it's rotten to sic the government on people; and it's rotten (and quite possibly unethical) to run the risk of siccing the government on someone using potentially inaccurate information. What would you do?