A former White Bear Lake man admitted Wednesday to killing his then-girlfriend’s 3-month-old daughter because the child wouldn’t stop crying.

“My stress levels were too high,” Austin B. Gustafson testified in court Wednesday. “I lost control.”

Gustafson, 28, of Pipestone, Minn., pleaded guilty in Ramsey County District Court to one count of first-degree manslaughter in exchange for prosecutors dropping the original second-degree murder count. He agreed to a prison term of 10¾ years and acknowledged that there were aggravating factors in the case.

The infant was injured on April 30, 2014, in the White Bear Lake apartment Gustafson shared at the time with his then-girlfriend. He called 911 and the infant was taken to a hospital, where she was placed on life support and died a few days later.

Gustafson testified Wednesday that when he awoke about 9:15 a.m. that day, the infant was in her swing crying. (Her mother had placed her there before going to work.) He gave her medication and tried to quiet her, but the crying didn’t cease. “She’d wake up screaming,” he said.

“Would you agree that’s something most babies do when they wake up?” asked Assistant Ramsey County Attorney Tanya O’Brien.

“No,” Gustafson said.

Gustafson responded to questions from O’Brien and his attorney, Aaron Haddorff, flatly, displaying no emotion. He told the court that he is receiving mental health treatment in jail and is on medication. The exact nature of his condition was not disclosed.

An autopsy showed that the baby died of a brain injury caused by deprivation of oxygen to her brain. She also suffered multiple rib fractures, bruises on her back and buttocks and hemorrhages on her head.

The baby’s mother attended the plea hearing and declined to comment afterward. O’Brien told the court that the mother was consulted about and approved of the plea deal.

Gustafson is scheduled to be sentenced on Feb. 18.

Chao Xiong