An 18-year-old Hilo man confessed to striking his 4-month-old son's head against a vehicle's door frame and waited a day before he sought medical attention, according to a police report.

Kainoa Poepoe-Vigil is charged with first-degree assault and was being held on $100,000 bail, the Hawai'i Tribune-Herald reported.

The baby was taken unconscious and unresponsive to Hilo Medical Center last Wednesday afternoon, bleeding from his nose. He was transferred to The Queen's Medical Center in critical condition.

A police affidavit said a doctor determined the baby suffered a skull fracture and bleeding in his brain.