user6935: 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?

user6939: I'm a cafeteria Buddhist, blending what I understand of it with what I understand of behavioral science and physics. Karma literally translates as "action."  
Newton's third law: for ever action, there is an equal and opposite reaction. So for a good action, there is a generally equal in magnitude good action coming back to you. For a bad action, likewise. These actions aren't necessarily for another day... or lifetime... to come. Actions could be immediate, in the way a waiter treats you, someone responds to a post or comment, you are apprehended by the law, and so on. 
Good actions beget good, and the more you do, the more you tend to be the recipient of good action. The good energy this produces within you and around you is a virtuous cycle with many benefits for health and well being. Bad actions beget bad. The world is very much a mirror for who you are being.
I see karma as a way of understanding the interaction of all the phenomena surrounding us and a guidepost for happiness and peace.

user43: It's not that the first offender's karma causes the second offender's karma. Instead, as my first teacher explained, in context of the victim-and-offender relationship karma works as a giant matchmaking machine, bringing the two together to rip the fruits of the seeds once sawn.
But you are right in that the mutual evil deeds don't cancel themselves out. Instead, karma has self-sustaining inertia, like a heavy spinning wheel - the more you spin it the more it spins you.
However, as Buddha has shown, not all of the future is determined solely by past karma. Our decision-making NOW is the most important factor.
In your example, both people, the original offender and the second offender, would commit their crimes due to 1) their own bad karma, PLUS 2) their own bad decision-making on the spot.
So "to stop the chain reaction", the only thing we can control is ourselves:
"Am I choosing to act out my previous pain, insults and injuries -- and by doing  thus to spin the wheel of evil? Or should the chain of evil stop on myself? Let me spin the wheel of love and compassion instead!"

user111: 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.

6935: <p>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. </p>

<p>My question is what would have to be done to stop this chain reaction?</p>
 6939: <p>I'm a cafeteria Buddhist, blending what I understand of it with what I understand of behavioral science and physics. Karma literally translates as "action."  </p>

<p>Newton's third law: for ever action, there is an equal and opposite reaction. So for a good action, there is a generally equal in magnitude good action coming back to you. For a bad action, likewise. These actions aren't necessarily for another day... or lifetime... to come. Actions could be immediate, in the way a waiter treats you, someone responds to a post or comment, you are apprehended by the law, and so on. </p>

<p>Good actions beget good, and the more you do, the more you tend to be the recipient of good action. The good energy this produces within you and around you is a virtuous cycle with many benefits for health and well being. Bad actions beget bad. The world is very much a mirror for who you are being.</p>

<p>I see karma as a way of understanding the interaction of all the phenomena surrounding us and a guidepost for happiness and peace.</p>
 43: <p>It's not that the first offender's karma <em>causes</em> the second offender's karma. Instead, as my first teacher explained, in context of the victim-and-offender relationship karma works as a giant matchmaking machine, bringing the two together to rip the fruits of the seeds once sawn.</p>

<p>But you are right in that the mutual evil deeds don't cancel themselves out. Instead, karma has self-sustaining inertia, like a heavy spinning wheel - the more you spin it the more it spins you.</p>

<p>However, as Buddha has shown, not all of the future is determined solely by past karma. Our decision-making NOW is the most important factor.</p>

<p>In your example, both people, the original offender and the second offender, would commit their crimes due to 1) their own bad karma, PLUS 2) their own bad decision-making on the spot.</p>

<p>So "to stop the chain reaction", <strong>the only thing we can control is ourselves</strong>:</p>

<p>"Am I choosing to act out my previous pain, insults and injuries -- and by doing  thus to spin the wheel of evil? Or should the chain of evil stop on myself? Let me spin the wheel of love and compassion instead!"</p>
 111: <p>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.</p>

<p>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.</p>
