A 31-year-old Peoria Heights man has been sentenced to 38 years in prison for shaking or striking his six-week-old son to death in 2012.

Reports indicate that a Peoria County judge sentenced Zachary Knowles Friday.

Under a plea agreement, Knowles pleaded guilty to a single count of first-degree murder this year. Under the deal, he faced up to 40 years in prison rather than up to 100 years.

The father told authorities two years ago that Asa Knowles became unresponsive after he was bouncing his son to calm him down. And in court, the defense portrayed Knowles as a good person who simply made a "serious, mortal mistake."

But prosecutors disputed that portrayal. They say autopsy results showed the injuries, including a fractured skull, weren't accidental.