People are rather silly about this age vs risk thing. Being old doesn't stop people being a risk. A 77 yr old or something was released in the states because they deemed him too old to be dangerous, he immediately murdered someone by stabbing them to death.
The only real thing you need to cause harm, is intent. It doesn't take any real strength to put a knife into someone, or, less often here, shoot someone. The thing that primarily puts people in danger of murder/attack, is being unwilling to hurt people vs the people who do harm being willing to hurt people. Strength doesn't usually come into it. An old geezer is still plenty strong enough to kill most people because most people don't go around prepared to be killed, keeping everyone 10m+ away from them, being armed, protected and ready to prevent themselves being hurt. Most people walk around as if almost everyone they'll ever see has no intent to hurt them and thus have nothing to fear and no reason to behave defensively. As such the people who want to hurt people mostly just need to walk up to who they want to kill and bam... game over.
What makes violent evil people capable of killing doesn't just go away with age, it goes away only from learning, teaching, therapy and even then you can only make a best judgement and can't be sure. Being old is a terrible reason for believing people aren't dangerous any more.