The man who fatally beat his fiancée's 16-month-old in Washington County in May 2017 has been sentenced to 25 years in prison after pleading guilty to second-degree murder.

Jonathon D. Wierstad, 29, of Willernie, was on probation for inflicting severe brain damage on a toddler in western Wisconsin when he killed Blake Holmquist.

With credit for time in jail since the boy's death, Wierstad, who was sentenced on Friday in District Court, will serve roughly the first 15½ years in prison and the balance on supervised release.

"Taking one's anger out on someone else is never OK," said County Attorney Pete Orput. "Taking it out on a totally defenseless baby offends the sensibilities of us all. No amount of prison time can adequately offset this defendant's actions."

Five months before Blake's death, Wierstad and prosecutors in neighboring St. Croix County, Wis., agreed to a plea of no contest after he caused permanent brain damage in 2014 to the 3-year-old son of Stacie Nanoff, a Hudson-area woman who was his girlfriend at the time.

He spent six days in jail in January 2017 for the injuries he inflicted upon Cedarius Nanoff and was put on probation for one year. St. Croix County District Attorney Michael Nieskes said his office agreed to the plea deal because "the facts in the case gave us some proof issues, and we made the decision that we thought was in the best interests of the community and in accordance with the wishes of the victim's mother."

Any consequence for Wierstad for violating the terms of his probation in Wisconsin would have to wait until his sentence is satisfied in Minnesota, Orput said.

On the day of Blake's death, police and paramedics arrived at Wierstad's home, where they found the boy unresponsive.

Wierstad told police that his fiancée, Alycia Holmquist, went to pick up her 7-year-old son from school, leaving him to look after her 3- and 5-year-old children and Blake. He said the 16-month-old fell down the stairs, but a doctor said the injuries were consistent with severe shaking.