Officer J.R. Smith, 35, told the judge at his hearing that he regretted what had happened.

"I'm sorry," he said with a voice that was barely audible.

Officer Smith and former Officer Gregg Junnier, 40, pleaded guilty to manslaughter as well as a host of charges relating to an attempted cover-up.

Both men are expected to face more than 10 years in prison.

A third officer still faces charges.

The charges followed a 'no-knock' drug raid on the home of Kathryn Johnston, 92, that went disastrously wrong.

An informant had described buying drugs from a dealer there, according to Police.

When officers prised off burglar bars and burst in without warning, Johnston fired a single shot back that failed to injure anyone.

They returned with 39 shots, striking her five or six times, including a fatal blow to the chest.

Injuries sustained by officers in the raid were due to friendly fire and not Johnston’s gun.

Assistant US Attorney Yonette Sam-Buchanan claims that although no drugs were found in Johnston's home, Smith planted three bags of cannabis in the home as part of a cover-up.

To get the warrant, officers told a judge that an undercover informant claimed that the home had surveillance cameras monitored carefully by a drug dealer named Sam.

After the shooting, a man claiming to be the informant told a television station that he had never purchased drugs there.

Atlanta Police Chief Richard Pennington reacted to the allegation by stating that he was personally uncertain whether the suspected drug dealer ever existed.

Pennington has ordered drug testing for nearly 1,800 officers and improved oversight of narcotics operations and the issuing of no-knock warrants.

The Reverend Markel Hutchins, a civil rights activist acting as a spokesman for Johnston's family, said the family was satisfied with the officer's admission of guilt.

"They have never sought vengeance. They have only sought justice," he said.