Apparently, much of the violence is directed at Jamaican natives who went abroad to work as expats and returned home to retire. The article says of returning retirees:
The country they left behind was poor, but relatively safe. It is still poor, but shockingly violent. This verdant island has one of the higher homicide rates in the world (emphasis added).The result has been a dramatic drop off in retirees returning home, which is a serious setback for the island's economy. Violence can cause a similar decline in tourism as there are other lovely islands in the Caribbean.
Some of the criminals have turned out to be police or soldiers. Do you suppose Jamaica will corrode into the chaos that is Haiti? I hope not for their sake.