“I can’t for a minute imagine what that must have felt like for him,” said the lawyer, Perry Moriearty, who was with Mr. Burrell when he left the Minnesota Correctional Facility-Stillwater in Bayport, Minn. “He looks forward to going home to his family and just living — it’s been an awfully long time.”

While before the pardons board, according to The Associated Press, Mr. Burrell spoke about his time in prison: “I started going in and extracting medicine out of the poison. The trials and tribulations I was going through, I tried to get something out of it.”

Mr. Burrell had twice been convicted of killing Tyesha Edwards, who was in sixth grade when she was fatally shot while doing homework and watching TV at her family’s South Minneapolis home. Gov. Tim Walz, who recommended Mr. Burrell’s commutation, told her family during Tuesday’s hearing that “there is nothing I can do to ease your pain, and it will not be made better,” according to The Associated Press.

“But we must act today to recognize the law in this area has changed,” he told the family. “Justice is not served by incarcerating a child for his entire lifetime for a horrible mistake committed many years ago.”

Ms. Edwards’s father and brother told The Associated Press that they opposed the release of Mr. Burrell. The Hennepin County Attorney’s Office declined to comment, and Ms. Klobuchar did not respond to a request for comment.

Ms. Klobuchar, who embraced a tough-on-crime message while trying to appeal to moderate voters in the Democratic presidential primary, was criticized by civil rights advocates and Black community leaders after The Associated Press’s investigation.

She was the Hennepin County attorney for eight years, including during the office’s first conviction of Mr. Burrell, in 2003. That conviction was later overturned by the Minnesota Supreme Court, which said an inadmissible statement by Mr. Burrell had been used at trial.