(CNN) In a plea deal with prosecutors, former South Carolina police officer Michael Slager admitted to using excessive force in the 2015 shooting death of Walter Scott.

Slager shot Scott in the back as the unarmed man was running away from Slager after a traffic stop. In a reversal from his previous account, Slager admitted in court Tuesday that he did not shoot Scott in self-defense and said that his use of force was unreasonable.

Scott's death sparked renewed "Black Lives Matter" protests after the 50-year-old became the latest in a series of unarmed black men killed by police

With his family and Scott's family present, Slager pleaded guilty Tuesday in US District Court in Charleston to a federal charge of deprivation of rights under the color of law. In exchange for the plea, state murder charges, as well as two other federal charges , will be dismissed.

The civil rights offense has a maximum penalty of life in prison. The plea agreement states that the government will ask the court to apply sentencing guidelines for second degree murder, which carries up to 25 years in prison. He was taken into custody after the hearing and will remain there until sentencing later this year.

Scott's mother said the sentence mattered little to her now that Slager had admitted responsibility.

"What made me feel good about it is that Michael Slager admitted what he did. That was enough years for me," she said in response to the question how much time she wanted Slager to serve.

"No matter how many years Michael Slager gets, it would not bring back my son," she said. "This is a victory for Walter. This is justice for the family, but this is just the beginning."

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The shooting

The plea marks one of the first resolutions of a high-profile police shooting under new Attorney General Jeff Sessions. He has ordered a review of police reform activities of the previous administration -- many of which were launched in response to police-involved shootings.

"The Department of Justice will hold accountable any law enforcement officer who violates the civil rights of our citizens by using excessive force," Sessions said in a statement Tuesday. "Such failures of duty not only harm the individual victims of these crimes; they harm our country, by eroding trust in law enforcement and undermining the good work of the vast majority of honorable and honest police officers.

Slager was an officer for the North Charleston Police Department when he pulled Scott over for a broken tail light. A few moments later, Scott ran away.

A foot chase ensued, and a bystander's cell phone video captured Slager firing eight times -- striking Scott five times in the back.

Slager initially said he feared for his life because Scott had grabbed his Taser -- but the plea agreement contains no such claim.

Slager's first attempt to use his Taser did not stop Scott. The second deployment dropped Scott to the ground but he got up and took off running again. As he was fleeing, Slager shot him.

"We hope that Michael's acceptance of responsibility will help the Scott family as they continue to grieve their loss," Slager's attorney, Andy Savage, said.

Lawyers for Scott's relatives said they accepted the plea deal.

"What these government officials did is they told Walter Scott and they told the Scott family, 'You matter.' And that is what we need to see all across the country, not just when there is a video," Justin Bamberg said.

Attorney Chris Stewart said the plea represented a rare show of accountability compared to other police-involved deaths that did not end in pleas or convictions.

"Today is rare. The Garners. The Blands. The Rice family. They didn't get this type of justice that we got today," said Stewart, who represents the family of Alton Sterling, who was shot by police in Baton Rouge, Louisiana.

"So it is a phenomenal day. And hopefully this will be the blueprint of future success for civil rights because it's got to change."

The explanation and the fallout

Protesters in North Charleston decry Walter Scott's death shortly after the shooting.

The North Charleston police chief fired Slager , and a state prosecutor filed a murder charge against him.

But in December, Slager's state murder trial ended in a mistrial after the jury failed to reach a verdict.

Prosecutor Scarlett A. Wilson vowed At the time to retry Scott. On Tuesday, Wilson said the state would not proceed further since the plea deal recognized the civil rights violation underlying Scott's death.

"While certainly the State charges addressed the killing of Mr. Scott, they did not squarely address the violation of Mr. Scott's civil rights by a police officer acting under color of law. It is essential that law enforcement and our community see the federal government address such an important aspect of this case," Wilson said in a statement.

"Now that Slager has pleaded guilty to a willful violation, admitted the facts we set out to prove and waived the right to appeal his conviction, a successive prosecution by the State is not necessary."

Anthony Scott said justice had been served with Slager's admission of responsibility. But he's still hoping for a life sentence.

"My brother was violated. He was gunned down running away and this gentlemen continued to stick to his story. But today -- he told the truth. He said he did it. And that's our victory and the healing starts today."