i) Trying to ban/confiscate guns misses the point. That's treating symptoms. Fixating on the weapon of choice fails to address the root cause. Why do some people turn to violent crime in the first place?
There are various reasons, not all of which are soluble.
One thing we know is that violent crime is overrepresented in certain intersecting demographic groups, by sex, age, and ethnicity.
Young men from stable two-parents homes are less prone to violent crime. Young men who stay in school are less prone to violent crime.
Conversely, violent crime is fostered by absentee fathers, a culture of dependency, high dropout rates, &c.
Partial solutions include school choice, so that kids aren't chained to failing schools. Plus welfare reform.
ii) In addition, as society becomes more secularized, it becomes more nihilistic. And that's coming from the top down, not the bottom up.
If kids are taught that there's no afterlife, no final judgment, no heaven or hell, no moral absolutes, that we are just fleeting, fortuitous collections of particles, then it's not surprising if some people act on that nihilistic philosophy. If you want people to behave better, you might begin by giving them something worthwhile to live for.
Atheism is a recipe for moral and existential nihilism. And we're beginning to see the results. Not just in mass shootings or urban violence, but at Planned Parenthood clinics. Likewise, we're poised for an exponential rise in euthanizing the elderly and developmentally disabled.