A federal judge sentenced a former Hawaii soldier Friday to the mandatory 10-year prison term for assaulting his 2-year-old son in 2011, inflicting permanent brain damage and blindness.

Marcel Reno Highwalking, 22, was living with his wife on Joint Base Pearl Harbor-Hickam when his son from a previous relationship arrived in August 2011 to visit for a few months. Highwalking’s wife was a service member. The boy had been living with his mother in Montana.

Highwalking told investigators that he struck and shook his son when he was frustrated.

On Oct. 25, 2011, the boy was comatose when Highwalking took him to the Pali Momi Medical Center emergency room. Doctors transferred the boy to Kapiolani Medical Center, where an examination revealed that the boy had fractures to his skull, spine, right arm and toe. Some of the fractures were 2 to 4 weeks old.

The boy also had damage to his brain, optical nerve and the retinas of both eyes — damage consistent with abuse trauma or shaken baby syndrome.

U.S. District Judge Leslie E. Koba­ya­shi called the abuse case one of the worst she’s seen as a federal judge. But she also said she thought that the mandatory 10-year prison term is excessive given Highwalking’s age, expression of remorse, military service, his own history of being abused and for admitting what he did when FBI agents confronted him. Initially, Highwalking lied about the injuries and blamed the boy’s mother.