Retanca Stafford has waited three months to find out if Fulton County's top prosecutor will indict the MARTA police officer who shot her son in the back.

"I don't know what to say or what to think," said the 38-year-old mom. "I have seen how they try to cover up for the police and I don't like it. Just gunning him down like that, something needs to be done."

District Attorney Paul Howard said he received the report Friday on the October killing outside the Vine City MARTA station and his public integrity unit is now trying to decide which witnesses to believe. Some witnesses put a gun in 19-year-old Joetavius Stafford's hands while others said he was unarmed, Howard said.

Meanwhile, Howard said that in an unrelated case in which Ariston Waiters, 19, was shot in the back by a Union City police officer in December, his office had not yet received the GBI report.

In the Stafford case, Howard said, “We have a number of different versions on whether he had a gun, when he had a gun and what he did with the gun. We have been working on it since it happened. Now that we have got the entire report we are going into overdrive so we can reach a conclusion.”

Rodney Stafford, the victim's brother, told Channel 2 Action News a fight had broken out after high school football games at the Georgia Dome and there was a gunshot as police arrived. He said his brother was unarmed and fleeing but stopped and threw up his hands at MARTA Officer Robert Waldo's command.

Rodney Stafford said his brother was shot twice on the ground, a claim that an autopsy was unable to confirm or dispute. The autopsy by the Fulton County chief medical examiner showed Stafford had been shot once in the chest and twice in the back.

Howard said investigators discovered a gun in the case, but he would not say where it was found or whether it had Stafford's fingerprints.

Howard said he was asking for any member of the public who witnessed the event or had video of the fight and police response to contact his office. "We haven't received any video and that is unusual in this age of cellphones," Howard said. "There were thousands of people out there that night."

Retanca Stafford said her son had never carried a gun. Other than being arrested for a fight at school and  for driving without a license, she said, he had never been in trouble with the law.

Howard said Stafford didn't have a significant record and had no known association with gangs, despite living in the Pittsburg neighborhood, home of the notorious gang 30 Deep.

"All I know is that when I asked him to do something, he did it, even if he didn't want to," Stafford said of her son.

She said the Dec. 16  killing of Waiters in Union City made her fear police were running amok and would not be held accountable.

An autopsy showed Waiters died of two gunshots to the back. He was fleeing police during a fight in a Union City subdivision after somebody had fired a shot into the air. No gun was found on Waiters.

Waldo, 31, has been assigned a desk job until the outcome of the Stafford investigation, MARTA spokeswoman Cara Hodgson said. MARTA has received the GBI report, which just sets out facts and does not make recommendations, but has not taken any other action against Waldo, Hodgson said.

Asked how long it would be before he decided whether to seek an indictment, Howard was uncertain. “We are trying to marry the eyewitness testimony with the physical evidence," he said.

Police are judged differently than ordinary citizens when they kill someone because of the nature of their job, said David Klinger of the University of Missouri-St. Louis, an expert on the police use of force.

The issue, he said, will be how a reasonable police officer would perceive and act in a certain situation -- which can be difficult to determine when you have differing witness accounts, darkness and police responding to a confrontation.

“Officers are permitted to make good faith mistakes," Klinger said.

In the Waiters case, "the family is just waiting for some answers," said Mawuli Davis, a lawyer representing the victim's family.

Davis said the most telling evidence in that case should be Waiters being shot in the back.  “I don’t know of a scenario where a person running away from you, with his back to you, is still a threat,” Davis said.