IMO: It seems that gang on gang violence only leads to more violence, and such violence seldom stays within the gangs. Once killing becomes the norm, it quickly becomes evident that family, friends, and other innocents make easier targets than armed opponents. Once one has killed the first time it gets a lot easier to do so again, and again, and negative consequences of killing anyone become less and less important.
I think that is right. The one difference which sometimes occurs in Caribbean countries is that these are much smaller communities - even if the police don't know who is involved, other people do - and eventually the growing tide of disapproval from friends and family has an effect.
But I am not a criminologist, and I am not pretending this is a universal truth. For example, the violence rages unabated in Trinidad and Jamaica, and probably will until the end of time. But certainly in BVI, when we have trouble flaring up with gangs, it usually does calm down after a while, usually without any arrests ever having been made.