IIRC it is called a crime under duress and is usually either excusable or justifiable in some states. For instance, if you are stuck in a blizzard, break and enter, and eat/steal items for survival....its an excusable crime. If someone places a bomb on you and tells you to rob a bank, you are under duress. HOWEVER, I'm not sure how it pertains to murder and accessory after the fact. I think that could be stretching it. I'll wait for more info. The article mentions the MOM of one of the YOUTS being the first to go to the Sheriff. Once these cretins turned on each other, the real story started to unravel.
Three people can keep a secret if two of them are dead.