Great! Then let's give him an incentive to "go straight" on his own, namely, safety. Rather than keeping him away from society, why don't we offer him opportunities within society to better his position without using violence?
Threatening him with violence isn't a working incentive. Criminals are threatened by institutionalized violence every day. Doesn't really scare them straight now does it? If you want to help, which I'm all for, you need early intervention in schools, extra resources dedicated to helping kids in danger. Social programs to help single parents. Early diagnosis and treatment of kids with mental disabilities. That's how you reduce crime.
Education, and help to find a job for those who already are committing crimes. Tools for them to handle their issues. That's what to do if you want to help people to "go straight".
None of the above is relevant for the topic however.
I see crimes as a result of social problems. Adding a lot of guns to the mix doesn't solve the problems. It attacks the symptoms, with a lot of extra bloodshed.