The city commissioned a report that found most violent crime is committed by a very small number of people.

https://dcist.com/story/22/02/18/majority-of-dc-homicides-driven-by-small-group/

”In Washington, D.C., most gun violence is very tightly concentrated on a small number of very high risk young Black male adults that have a shared set of common risk factors,” says David Muhammad, the executive director of the National Institute for Criminal Justice Reform. “This very small number of high risk individuals are identifiable. Their violence is predictable and therefore it is preventable.”

I presume the problem doesn’t suddenly begin when someone becomes an adult, so that tracks what with your friend observed.