Markus Kaarma was sentenced to 70 years in prison on Thursday for shooting an unarmed German exchange student to death last year.

Kaarma killed 17-year-old Diren Dede just after midnight on April 21, after setting a trap in his garage. After he caught Dede in his garage, Kaarma fired four rounds from a shotgun, striking the teen in the shoulder and head. Dede, who was unarmed, later died.

Defense attorneys argued that Montana's "castle doctrine" gave Kaarma the right to protect his home with deadly force. A Montana jury disagreed, and in December Kaarma was found guilty of deliberate homicide.

Missoula district judge Ed McLean ruled that Kaarma won't be eligible for parole for 20 years. From the Missoulan:

"You pose too great a risk to society to be anywhere else but the Montana State Prison. Good luck to you, son," the judge said.

"(Your anxiety) doesn't excuse the anguish you have caused. Anxiety isn't an excuse," McLean said. "You didn't protect your residence, you went hunting. And here you have a 12-gauge shotgun that's loaded. Not to protect your family but to go after somebody."

"You are angry at the world and it's evident in your behavior," he added.

Kaarma's attorneys say they'll appeal the ruling. For more about the shooting and Dede's life, read Der Spiegel's deep-dive into the case.