A Blaine man has been arrested and booked into Whatcom County Jail on investigation of assaulting his infant son, who was in critical condition Friday, Nov. 2, at Harborview Medical Center with head and brain injuries.

Melvin C. Johnson, 31, was arrested on one charge of assault of a child in the first degree. Blaine police said Johnson admitted on Friday that he had thrown the 4-month-old boy to the ground Wednesday.

Washington State Department of Social and Health Services notified police on Wednesday that the boy's mother had taken the unresponsive child to St. Joseph hospital in Bellingham. Hospital staff determined that the child had also suffered previous injuries, including fractured bones and head trauma, police said. An investigation got under way, and the child was airlifted to Harborview in Seattle.

The investigation is continuing with assistance from DSHS, Seattle Police, Bellingham Police and the Whatcom County Prosecutor's Office.