MADISON, Wis. (AP) — A judge on Friday sentenced a man convicted of killing a University of Wisconsin-Madison student in 2008 to life in prison without parole.

David Kahl, 56, pleaded guilty in October to first-degree intentional homicide in the strangulation and stabbing death of 21-year-old Brittany Zimmerman. The charge carries a mandatory life sentence; the only question was whether Dane County Circuit Judge Chris Taylor would make Kahl eligible for parole at some point.

The Wisconsin State Journal reported that Kahl told Dane County Circuit Judge Chris Taylor before she handed down his sentence that he didn’t want parole.

“I would like to apologize to everybody, especially the Zimmerman family,” Kahl told the court. “I took away Brittany’s 21-year-old life, family that she could have had. … And I’m accepting the punishment that I’ve got coming.”

Taylor told him that his regret was coming too late. Kahl obstructed investigators for years before confessing in the face of newly discovered DNA evidence against him.

“I do doubt that you understand fully the magnitude of your actions,” she said. “I don’t think you do.

Zimmerman, a senior microbiology student, was engaged to be married when she encountered Kahl on April 2, 2008. Kahl had been awake for eight days and taking methamphetamine and crack when he knocked on the door to her apartment asking for money to fix a flat tire. He was actually looking for money to buy drugs, according to court documents.

He was in the apartment’s bathroom when he heard Zimmerman call police. He told his mother in an Oct. 22 phone call from jail that he came out of the bathroom and “snapped.” He said he threw her down and strangled her with a T-shirt. When he noticed she was still alive he stabbed her 19 times, according to Taylor, and Kahl’s confession.

Kahl told his mother in the October call that he blamed emergency workers for Zimmerman’s death, saying she’d be alive if they had responded to her 911 call faster.

Her death led to an investigation into the Dane County 911 center. A dispatcher failed to hear a scream on the call and failed to call Zimmerman back after the connection was cut off. The county ultimately added 11 new operators and a new director.

Investigators questioned Kahl multiple times but he gave them conflicting information or changed his story. But as DNA technology improved over the years analysts were able to confirm that Kahl’s DNA was on Zimmerman’s clothing, according to a criminal complaint.