Charleston, South Carolina (CNN) Michael Slager, the former South Carolina police officer who shot and killed Walter Scott, was sentenced Thursday to 20 years in federal prison, a decision the Scott family said gave it a "sense of justice."

"This is an historic day for civil rights, in particular for officer-involved shootings," said Chris Stewart, one of the Scott family's attorneys, at a press conference following the sentencing.

US District Court Judge David Norton made his decision after hearing emotional statements from members of both families. Norton earlier Thursday had said the "appropriate underlying offense" for Slager, who is white, was second-degree murder.

Scott's family has repeatedly expressed forgiveness to Slager, who said that he was thankful for that. But the victim's relatives were glad to see the officer held accountable.

"We are hurt," said Anthony Scott, Walter's brother, "and we do have some type of passion for the Slager family, in that they have to suffer as well. And we do forgive Michael Slager for what he did. But yes, we did want justice for my brother, and we feel that we have gotten a sense of justice."

At the time of the shooting, Scott was only the latest black man to be killed in a series of controversial officer-involved shootings that prompted "Black Lives Matter" protests and vigils.

Photos: Reactions to Walter Scott shooting Joe Gilliard looks over a fence April 9, 2015, at the spot where Walter Scott was shot and killed by a police officer April 4 in North Charleston, South Carolina. The officer, Michael Slager , has been charged with murder in the fatal shooting of Scott , an unarmed 50-year-old. Video captured by a bystander showed Slager shooting Scott as he ran away. Hide Caption 1 of 8 Photos: Reactions to Walter Scott shooting Chasyn Carter, right, embraces Candice Ancrum during a candlelight vigil outside North Charleston's City Hall on Wednesday, April 8. Hide Caption 2 of 8 Photos: Reactions to Walter Scott shooting Charleston County Sheriff Al Cannon holds a candle as he joins the City Hall protest on April 8. Hide Caption 3 of 8 Photos: Reactions to Walter Scott shooting Darrell Mikell, Aaron Moses, Justin Lewis and Quin Dalton stand April 8 near the site where Scott was shot and killed. The person in the background is unidentified. Hide Caption 4 of 8 Photos: Reactions to Walter Scott shooting Protesters interrupt a press conference with North Charleston Mayor Keith Summey on April 8. Hide Caption 5 of 8 Photos: Reactions to Walter Scott shooting People protest Scott's shooting as they rally outside North Charleston's City Hall on April 8. Hide Caption 6 of 8 Photos: Reactions to Walter Scott shooting Some of those rallying outside North Charleston's City Hall held signs and wore shirts that said "Black lives matter." Scott was black. Slager is white. Hide Caption 7 of 8 Photos: Reactions to Walter Scott shooting Scott's cousin Barbara, right, and her mother, Evaliana Smalls, lay flowers at the lot where the shooting took place. Hide Caption 8 of 8

Life sentence sought

Federal prosecutors sought a life sentence, arguing Slater, then a North Charleston police officer, had committed second-degree murder and also should be punished for obstructing justice by providing the South Carolina Law Enforcement Division with false statements.

Slager, 36, shot Scott five times in the back "for running away, simply for having a broken taillight," Jared Fishman of the Justice Department's Civil Rights Division told the court in his closing statement this week.

It's "time to call it what it was -- a murder," Fishman said, specifying second-degree murder.

But defense attorney Andy Savage argued that while Slager's actions were criminal, they did not amount to murder. The appropriate offense was voluntary manslaughter, Slager's attorneys said.

A probation officer had recommended Slager be sentenced to 10 to 13 years in prison.

Norton recognized that neither the Scott family nor the Slager family likely would be pleased with his punishment, adding that sentencing is the hardest facet of his more than 27 years on the bench. Slager has 14 days to appeal.

In a statement, Attorney General Jeff Sessions expressed his condolences to the Scott family and stressed the duty police officers have to uphold the law and protect citizens.

"Officers who violate anyone's rights also violate their oaths of honor, and they tarnish the names of the vast majority of officers, who do incredible work," he said. "Those who enforce our laws must also bide by them -- and this Department of Justice will hold accountable anyone who violates the civil rights of our fellow Americans."

Two families changed forever

Before the sentence was announced, Scott's family addressed the court and gave the judge their victim impact statements.

Judy Scott broke down in tears as she recalled the memory of her son.

"If you met him, you would like him," she said. "I didn't know anyone who didn't like him."

Speaking to Slager, Scott also said she forgave the former officer, a sentiment echoed by Walter Scott's brother, Anthony Scott.

"I miss my brother, and our family will never be the same," he said. "Until I got the help I needed, it helped me to release the pain of losing my brother. God gave forgiveness in my heart for Officer Slager."

Members of Slager's family also provided statements to the court in an effort to lessen the sentence. They shared with the court a portrait of a young man who became a police officer and went into public service out of an intense desire to help people.

His mother, Karen Sharpe, told the court he was a wonderful son, husband and father. "This will be in his heart for the rest of his life and will never, ever go away," she said through her tears. "He's a very, very good person and he'll think of this for the rest of his life."

Slager's wife, Jamie, asked the judge for mercy for her husband. "My heart breaks that things cannot be changed," she said.

Slager, looking haggard in a gray-and-white prison jumpsuit with his wrists shackled to his waist, gave his own testimony. For the past 31 months, he said, he had thought about the moment he opened fire.

"Walter Scott is no longer with his family, and I'm responsible for that," Slager said, adding the Scott family would be forever changed without Walter.

"I'm standing here before you taking responsibility for my actions."

The Scott family said at the subsequent press conference that Slager had sought to make amends with them.

"He apologized to the family," said Rodney Scott, another of Walter's brothers. "He called each and every last one of our names in court today and apologized. So who are we not to forgive?"

The attorneys praised Norton's decision, but said it was "only the beginning."

"Yes, this is a sense of justice here," said Justin Bamberg, an attorney and state legislator. "But the fight for justice can't stop here, and we all owe it to ourselves and those around us to continue to fight to make the system better."