MINNEAPOLIS (WCCO) — Attorneys for Jacob Wetterling’s killer say he has struggled with the secret of what happened for nearly 30 years.

In a court filing Thursday, they said 53-year-old Danny Heinrich still cannot understand how he did something so heinous. Two months ago, Heinrich admitted he kidnapped Wetterling from St. Joseph in 1989 and led the FBI to the 11-year-old’s body. As part of a plea deal, a judge will send Heinrich to prison for receiving child pornography next week.

Ahead of that, Heinrich’s public defender wrote, “the truth is he is just a man; a man with human failings. He feels a great deal of guilt and remorse for the pain and anguish he has brought the Wetterling family.” The filing also says Heinirch still hopes he can “somehow convey how sorry he feels for the terrible crimes he has committed.”

The U.S. Attorney for Minnesota wants the judge to send Heinrich to prison for 20 years.