Won't bad karma cause a chain reaction? So consider the situation where you did something bad like killing someone (or something less serious) which means that you now have bad karma. So now something bad needs to happen to you, considering all things this thing will statistically caused by another person doing something to hurt you (physically or mentally) which adds to their bad karma and so on. 

My question is what would have to be done to stop this chain reaction?
Your bad Karma does not cause bad Karma for others. If another person gets a mindset to kill, it's not a result of your bad Karma. It's a result of his own aversion and volition. But your bad karma can place you at the wrong place at the wrong time.

ex: A crocodile might attack anyone who gets into the water. Your bad karma can place you at the river when the crocodile is waiting to grab a meal. 
Coconuts fall down from coconut trees whether you killed someone or not. But your bad Karma can place you under a coconut tree when a coconut is falling down.