Who's fault is it?

Most of you have heard about how US troops gunned down Reuters cameraman Mazen Dana after mistaking him for an Iraqi guerilla with a rocket-propelled grenade launcher.

Reports state the troops shot first and attempted to resuscitate him later.


According to the Boston Globe:

Eighteen journalists have died in Iraq from hostile fire and accidents. Five have been killed by the US military.

Dana's family wants justice. How do you punish the US troops in this situation? What is a reasonable expectation of justice? Should reporters be in Baghdad?