LEWISTON, Idaho (AP) — A northern Idaho man accused of killing his infant son by shaking him has pleaded not guilty to first-degree murder.

The Lewiston Tribune reports that 20-year-old Cody Gossage made the plea Thursday in 2nd District Court.

Authorities say that officers on Oct. 29 responded to a call for help and found 5-month-old old Jordan Bigman-Gossage unconscious and not breathing.

He was taken to St. Joseph Regional Medical Center in Lewiston, but then flown to Seattle within a few hours for advanced treatment because of severe brain trauma. He died two days later.

Gossage says his son sustained injuries in a bathtub fall.

But medical doctors told police the child's injuries weren't consistent with a bathtub fall, and that he had rib fractures consistent with an adult's hard grip.