Manuel ‘Tortuguita’ Paez Terán was shot and killed in January while protesting construction of police training center

No criminal charges will be brought against state patrol troopers in Georgia who shot and killed an environmental protester at the site of a huge new public safety training center for law enforcement and others in the Atlanta area, known as “Cop City”.

The district attorney pro tempore made the announcement on Friday, almost nine months after Manuel Paez Terán, nicknamed Tortuguita, 26, was killed in January during protests against the development.

They were one of dozens of activists camped in a public park in mid-January protesting against the $90m police and fire department training center planned for part of the South River forest less than a mile away, when law enforcement opened fire.

It was the first time in US history that police killed an environmental activist while they were protesting.

The Stone Mountain judicial circuit district attorney, George Christian, announced his decision not to pursue charges in a news release. He was appointed to review the Georgia bureau of investigation file on the 18 January shooting of Paez Terán after the DeKalb county district attorney, Sherry Boston, recused herself from the case.

The use of deadly force by Georgia state troopers who shot and killed the activist was “objectively reasonable” and, hence, no charges will be sought against them, the prosecutor said.

Opponents of Cop City had occupied an 85-acre tract of forest that is being developed for the massive facility where Paez Terán was killed.

State troopers were part of an “enforcement operation” at the site. When the activist refused to come out of a tent, the troopers fired a pepper-ball launcher and Paez Terán responded by firing a handgun four times through the tent, hitting and seriously wounding a trooper, Christian’s release said on Friday. Six troopers fired back, killing Paez Terán. An independent autopsy commissioned by their family, however, revealed that there was no gunpowder residue on Paez Terán’s hands and they had their hands raised at the time of the shooting.

The private autopsy also found that Paez Terán suffered at least 57 gunshot wounds. The DeKalb county medical examiner had concluded the death was a homicide, although it did not draw a conclusion about whether Paez Terán’s hand were in the air.

An inquiry into the killing has been marred by contradictory information released by officials.

A further extraordinary turn of events came when 61 protesters were charged under Georgia’s racketeering (Rico) law, as laid out in a 109-page indictment released last month – a law usually used against organized crime groups, like the mafia. It is the largest criminal conspiracy case ever leveled against a protest movement.