Seems a bad decision.
Even manslaughter will be difficult to convict.
Political charges without investigation is stupid.
Except for a couple of things. One, Atlanta police policy says you do not shoot fleeing suspects in the back. Two, the shooting does not seem to meet the guidelines for use of deadly force on fleeing suspects that the Supreme Court laid out in two cases, Tennessee v. Garner and Graham v. Connor. The court ruled that use of deadly force on a fleeing suspect was not justified unless "the officer has probable cause to believe that the suspect poses a significant threat of death or serious physical injury to the officer or others." Brooks was fleeing. He was unarmed except for the Taser which the officer knew had been fired twice and therefore posed no further threat. Shooting him did not meet the requirements of the Garner decision. Add to that the fact that witnesses stated that once he shot Brooks Rolfe shouted "I got him". And the fact that there apparently video of him kicking Brooks' body. And the fact that they didn't call for medical assistance for an period of time. All adds up to the 'depraved indifference' that the prosecution needed for the murder charge. Finally the other officer, Brosnen, is turning state's evidence. It doesn't look good.
Political charges without investigation is stupid.
You assume no investigation was done. They have video out the wazoo. They have the ballistics report and the autopsy. They had more than enough to charge.