In the courtroom, Brok Junkermeier is a quiet 19-year-old with close-cropped hair and glasses. When prosecutors show photos of Lila Warwick, the 79-year-old he allegedly killed, he turns his head and lowers his gaze.

But in a videotaped interview shown to jurors Tuesday in Willmar, Minn., a shaggy-haired Junkermeier casually admitted to killing Warwick, using his own body to show where he stabbed her "six, seven times" after choking her and breaking her neck.

"One, two, three, four," Junkermeier said, hitting points on his chest and abdomen.

Junkermeier has pleaded not guilty to first-degree murder charges for allegedly carrying out the July robbery and attack prosecutors say he planned with Warwick’s grandson, Robert Inocencio Warwick, 18. Prosecutors say Junkermeier forced Lila Warwick to write him a check for $1,500 before killing her, returning to the house later that day to steal her safe.

Two days after Lila Warwick's death, investigators approached Junkermeier at his work and drove him to the sheriff’s office, where they interviewed him for nearly four hours. At first, he denied being involved in Lila Warwick's death, saying the check was for chores he had done around her house.

But after investigators implied that Lila Warwick had recently installed security cameras in her house, Junkermeier confessed, saying, "I killed Lila Warwick."

He described not only the attack in late July but the two times he had been to the house before, with the same intention. The first time, "Robbie" Warwick and another teen accompanied him, he said, rifling through the things in Lila Warwick’s car. A noise scared them off. The next time, a solo Junkermeier saw a light on, so he left.

Junkermeier also told investigators about returning to Lila Warwick's house on the east edge of Willmar to grab her safe. Robert Warwick, then 17 years old, came inside, too, and was disturbed by all the blood, he said.

"He keeps saying, 'Oh my god.'" Junkermeier said in the video. "He doesn’t want to look at anything."

Early in the interview, Brad Redmond, a detective sergeant with the Kandiyohi County Sheriff's Office, suggested to Junkermeier that Robert Warwick was the crime's "mastermind," an assertion repeated in complaints and other court documents. (Warwick's trial has not yet been scheduled.)

"He’s the planner, he’s the mastermind, he’s the organizer," Redmond said. "I’m thinking he’s the organizer of this." Later, he added, "Don’t take the fall for anybody else on this."

Junkermeier then told them that Robbie had suggested killing his grandmother because he didn't like her and she had a lot of money. "It wasn’t my plan," Junkermeier said. "You know it’s not my plan. It’s not even my grandma."

Outside the courthouse Tuesday evening, Junkermeier's attorney Kent Marshall repeated his assertion that while Junkermeier killed Lila Warwick, that doesn't mean he's guilty of the two charges -- first-degree, premeditated murder and first-degree murder in the course of a burglary.

"No question about what he's done. You've heard the evidence," Marshall said. "Clarence Darrow said we might hate the sin but never the sinner.

"And I think that's important to remember here."