Jonathon Wierstad called 911 in May to report that his fiancee’s toddler had fallen down a small set of carpeted stairs at their house in Willernie and was having trouble breathing.
Wierstad, 28, was arrested later that night after doctors at Gillette Children’s Specialty Healthcare in St. Paul said the 16-month-old’s injuries were “not consistent with a fall down stairs,” according to a criminal complaint filed in Washington County District Court.
The toddler, who had been on life support since the May 11 incident, died at 3:44 a.m. Saturday at the hospital. Wierstad was charged today with second-degree murder; he previously had been charged with first-degree assault with great bodily harm.

“Cases like these that involve innocent and defenseless children are particularly difficult to investigate,” said Commander Andrew Ellickson of the Washington County sheriff’s office. “Our heart goes out to the family of the child.”
Wierstad, who is being held in the Washington County Jail, appeared in court Monday. Bail was set at $2.5 million without conditions.
According to the criminal complaint, the toddler suffered a closed-head injury “that resulted in massive swelling and bleeding on his brain.”
Surgeons who performed emergency brain surgery reported that the “swelling of his brain was so extensive that part of his skull was removed to relieve the pressure,” the complaint states. “The swelling remained so extensive that the surgeon was unable to reattach the skin and was forced to sew mesh to (his) head in order to cover the swollen area. The surgeon concluded that (the toddler) would suffer permanent injuries at the very least and could possibly die from the injury.”
On May 11, Wierstad was babysitting for the toddler and two other small children — a 3-year-old and a 5-year-old who are cared for by his fiancee. His fiancee told officials that she had run out to pick up her 7-year-old son from school and left Wierstad in charge of all three children; Wierstad is not the biological father of either boy, the complaint states.
Wierstad told officers that he walked down the stairs, forgot to close the baby gate and “shortly thereafter … heard a thud,” the complaint states. “He claimed that he found (the toddler) lying at the bottom of the stairs, thereafter taking a breath every 8 seconds. The home is a split-entry, and the newly carpeted stairs that defendant claimed (the toddler) fell down consisted of seven total stairs. The landing was covered with a mat.”
The surgeon who performed the surgery concluded that the child’s injuries were inconsistent with a fall down stairs as the “injury requires significant acceleration and deceleration,” the complaint states. “The injury … is more akin to the type of head injury a child would suffer in a high-velocity car accident without restraints or severe shaking.”
The murder charge comes five months after Wierstad pleaded no contest to substantial battery to a child in St. Croix County in 2014. He is serving felony probation in connection with that case.
St. Croix County prosecutors charged Wierstad in April 2014 with causing permanent brain damage to his then-girlfriend’s 3-year-old son during an incident at their house in Hudson, Wis. The boy sustained a brain bleed that medical officials said was consistent with child abuse or a high-speed auto crash.
Wierstad initially told police that the boy had fallen in the bathroom while he and the boy were left alone with each other, according to the criminal complaint filed in St. Croix County District Court. In a second interview with police — during which he was confronted with doctors’ suspicions that the injuries were from abuse — Wierstad changed his story. In that account, he told police he had been throwing the boy in the air when he accidentally dropped him. The boy then later fell in the bathroom, he said.