The charge against Timothy Kenneth Lundberg, 31, of Bemidji, has been amended to second-degree murder without intent, a serious felony.
Lundberg allegedly caused fatal injuries to a 7-month-old infant on Dec. 18, when the child was in his care.
Lundberg was arraigned on the new charge Tuesday morning in Beltrami County District Court. Bail was set at $500,000 without conditions and $250,000 with conditions that include he not have contact with his co-defendant, Brenda Kala Hertel, or the victim's family.
Hertel, 22, was charged in January with felony neglect or endangerment of a child.
Lundberg had been charged in January with first-degree assault causing great bodily harm.
The infant, Ayven Jayce Shepard, died Feb. 4, as a result of the injuries he suffered Dec. 18, according to the new criminal complaint.
According to the new criminal complaint, Lundberg on Jan. 24 told Hertel's friend that he had "just snapped" and that he shook Ayven Shepard because he would not stop crying. Lundberg reportedly made the friend promise not to relay the conversation.
The friend provided a statement to law enforcement on Feb. 5, the day after Ayven Shepard died.
According to the criminal complaints:
At 5:08 p.m. Dec. 18, Beltrami County officers were summoned to the Hertel-Lundberg residence at 5653 Alps Court N.W. on a report of an unresponsive infant.
Ayven Shepard, then 7 months old, was taken to North Country Regional Hospital emergency room where he was diagnosed by Dr. Beverly Richter as having massive left side head trauma. He was air-lifted to Minneapolis Children's Hospital, where he remained until his death last week.
The baby's mother, Krysten Shepard, had hired Hertel and Lundberg to care for him and another child from 7:30 a.m. to 5:30 p.m. Monday through Friday beginning Oct. 30.
The mother reported that Ayven was happy and healthy when she left him with the caregivers the morning of Dec. 18. Hertel had been out of the home most of the day, returning shortly before 4 p.m. when the baby had already been injured.
Krysten Shepard received a call at 5:07 p.m. from Hertel saying she couldn't wake the baby. Hertel asked if she should call 911, and the mother told her to do that.
A physician at the Minnesota Resource Center also evaluated Ayven's condition in relation to physical abuse and reported, "The baby has sustained devastating, life-threatening head trauma, including a large subdural hematoma, a major brain injury. ... These findings are consistent with violent, high force trauma. Injuries this severe have caused the baby to be symptomatic immediately or very shortly thereafter the traumatic event. His overall prognosis remains extremely grave."
Beltrami County Sheriff's investigators determined that Hertel was aware of the baby's condition at about 4 p.m. Dec. 18, but she did not call law enforcement for more than an hour. The Minnesota Resource Center physician reported that the baby's injuries increased during the hour he went without medical care.
Hertel and Lundberg did not provide any "reasonable" explanation for the baby's injuries.