Spokane Police have arrested 23-year-old Joshua Burnett on a charge of second-degree murder in the death of a Spokane toddler last month. Burnett, who was the child’s mother’s boyfriend at the time, was left alone with the 18-month-old, police Commander Brad Arleth said at a news conference this afternoon. After injuring the toddler, Rylee Castner, Burnett mocked the boy because he was unable to hold his head up, Arleth said. Castner died March 31 from blunt force trauma to his head, according to the Medical Examiner’s office. His death was ruled a homicide. Arleth said the injury occurred at the boy’s mother’s home. Burnett was at the home frequently, police said, but didn’t live there. Castner’s “injuries were inflicted on purpose,” Arleth said.