How can I promote justice for the innocent without revenge?

Kids in classroom killed for no reason.

A midnight showing of an adventure movie ends in tragedy.
A bomb explodes at the end of a race, erasing smiles of elation, maiming and killing dozens.

We rise up as a nation full of individuals with one word on our lips. 
Justice.

We don’t want the guilty to go free after so ruthlessly changing the lives of the innocent. And we grasp for new laws and regulations. We want someone to do something, anything for the sake of justice.

And then there’s vengeance.  I’ve tasted it in my mouth, it’s full of sweetness, and mirth. It satisfies for a while, but leaves me hungry.

We have comic book heroes who exact the right amount of justice to the evil doers. But it’s not so clear. The guilty walk and the innocent seem to pay. And there’s no one in tights to set it all right.

And the dark twin, revenge,  has few equals. There’s no gray in that matter. It’s simple in its swift retort and leaves no question.

I know that I need to God judge. And that’s a hard thing to do when I feel so helpless. It seems like such a cop-out, to turn over my passion for payment to Him. 

I want to take things into my hands. But honestly, I have such a lousy track record at that, no wonder I rarely get the opportunity. 

There is a better justice to seek out.

…“and if you spend yourselves in behalf of the hungry,  and satisfy the needs of the oppressed,then your light<sup value='(B)’> will rise in the darkness, and your night will become like the noonday. (Is 58.10)

Is the answer to turn our anger and our hurt to solving the pain of others?

What are your thoughts on justice? How do you sort out vengeance, revenge and mercy?