It's popularily known the rise in violence and gun related homicides in the 1980s-1990s coincided with the explosion of crack cocaine (and a lesser extent heroin) and the proliferation of modern street gangs as we know them today (ie. bloods, crips, bd, gd, etc) in urban ghettos.

It's not difficult to find stats showing the vast majority of victims of violent crime happen in the same neighborhoods where drugs and drug sales coexist. Whether or not it's directly related it's at least a significant driving factor financing violent criminals and intertwined into related cultures as 'respected' professions.