He lay in wait in the dark basement, biding his time until his victim came home and fell asleep, nervously listening as a dog barked upstairs, wondering if the voices he heard were on the TV.
Finally, Aaron William Allen walked up the stairs to a bedroom where Brandon Horst lay sleeping. He pointed a gun -- given to him by Horst's wife -- and pulled the trigger.
Allen, who pleaded guilty in Ramsey County District Court to killing Horst at his home in the 400 block of Bellows Street in St. Paul, was sentenced Tuesday to 40 years in prison. It was the maximum allowed by law.
He did it, he testified, because Heather Horst claimed her husband beat her and killed their unborn baby.
She offered Allen $100,000 of the life insurance she said she would get from her husband's policy.
Allen, 26, of South St. Paul apologized to the Horst family Tuesday for the pain he has caused. He expressed the same sentiment to his own family.
"I wish I would have asked for your help," he said. "I wish I would have done the right thing."
Brandon Horst was 25 when he died of a single bullet wound to the head Aug. 5. The member of the Minnesota Air National Guard knew at age 16 that he wanted to join the military, his mother said. He served in Saudi Arabia.
Heather Leann Horst, 25, was convicted of first-degree premeditated murder and sentenced May 27 to life in prison without parole.
Although Allen took responsibility for the murder, that does nothing to ease the Horst family's loss, said Ramsey County District Judge John Guthmann.
"Brandon Horst went overseas to serve his country. He went overseas to serve you," only to be met by Allen's "incredible cruelty and cowardice," he told the shooter.
"It does not matter that you may have been manipulated or encouraged along the way," the judge said.
At Heather Horst's trial, prosecutors argued that she had a lover and wanted out of her marriage. But the only way she could think of to get that was by murder.
"I want him dead," she had told her friends. She began telling Allen in June 2013 about her husband's alleged abuse, though Allen never saw any marks on her. When she arrived at Allen's apartment the morning of Aug. 4, she told him and others that Brandon Horst had caused a miscarriage.
"I saw red," Allen testified at his plea hearing. He had been abused physically and sexually by a stepfather as a young child.
They arranged for two friends to help him kill Horst. The two would hold him down while Allen slit his throat. That plan unraveled when the other two men bailed out. Instead of a knife, Allen would use Heather Horst's pistol, which she removed from a wine cabinet in her dining room. She left the house in the evening while Allen waited for her husband to get home from work. About 12:30 a.m. the next day, Allen shot Horst. He was later pronounced dead at the scene.
Guthmann ordered Allen to pay $1,300 in restitution to Brandon Horst's mother and $6,500 to the Minnesota Crime Victims Reparations Board for funeral expenses. Guthmann dismissed a charge of first-degree premeditated murder against Allen, citing his cooperation with the prosecution of Heather Horst.
Brandon Horst's mother, Brenda Horst, said through tears that she and her firstborn were training to do a 5K run together when he was killed. A 20-year veteran of the Army Reserves herself, she was exercising regularly and eating well. Now, she said, she doesn't get exercise and can't sleep, "because the grief, sorrow and anger are overwhelming."
After the hearing, she said she was "still processing" Allen's statement of remorse.
"I know I will never find forgiveness in my heart for him," she said.
Brandon's father, Mark Horst, said he wasn't sure if Allen was sincere. "He's told so many lies."
Several members of Allen's family attended the courtroom hearing, including his mother, father, siblings and an aunt.
Allen's mother, Jacqueline Woelfel, said after sentencing that her family wanted to express their remorse to Brandon Horst's loved ones.
"We haven't been allowed to give our sympathies," she said. They were sorry for what the relatives of Heather Horst were experiencing as well, she said.
As for her son, "There's more to Aaron than what was said," Woelfel said. "He has genuine sympathy and remorse."