A 21-year-old father charged with manslaughter in the death of his 5-month-old son admitted to violently shaking his baby when he became upset when his son was crying while the father was trying to relax and play video games at their home in Kapolei, according to a police affidavit.

Huakai Kalamau, also known as Huakai Hookelelehiatane Self, made his initial appearance today at District Family Court in Honolulu before Judge Linda Martell via video conferencing from the courthouse cellblock.

Kalamau has been charged with manslaughter — a class A felony punishable by up to 20 years in prison — in the alleged shaken baby syndrome case. His bail is set at $300,000.

The Honolulu Medical Examiner’s Office has not released the baby’s name at this time. Family members on social media identified the baby as Ali’i Kalamau.

Police and Emergency Medical Services responded to a call of an unresponsive baby in the parking lot of the Kaiser Permanente Kapolei Clinic at 599 Farrington Highway just after 6:20 p.m. Monday.

When they arrived, an emergency medical technician observed Kalamau performing cardiopulmonary resuscitation on the baby. Police said the baby was taken by ambulance to The Queen’s Medical Center-West Oahu in critical condition where he was pronounced dead.

An autopsy revealed the baby had severe internal injuries that include a fracture to his left collarbone, subdural hemorrhaging, hemorrhaging to both optic nerves, thoracic spine fracture and rib fractures, according to new court documents filed today in District Court.

Kalamau initially told police that he was feeding his son formula when he noticed his son stopped breathing. His sister-in-law drove them to the Kaiser Permanente Kapolei Clinic but the facility was closed.

Kalamau performed CPR on his son in a grassy area in the parking lot until an ambulance arrived.

During an investigation into the baby’s death, police said Kalamau agreed to take a polygraph test. At the end of the examination, he allegedly admitted he wasn’t truthful in his initial statement to police.

Kalamau then told police he was tired and “just wanted to relax” and play video games after a weekend of drill duties for the U.S. Army Reserve, the affidavit said. He also told police he was under stress because of financial struggles.

On Monday, the baby was in his playpen while Kalamau played video games online with his friends. About two hours after Kalamau’s wife left for work, the baby woke up and began to cry.

Kalamau told police he allegedly became upset and swiftly picked up his son from the playpen, causing the baby’s upper body to bend backward. As the baby cried louder, Kalamau began “violently shaking” his son between 30 and 60 seconds and stopped after the baby became limp and unresponsive, police said.

Kalamau performed chest compressions in attempt to revive him.

He told police he just wanted his baby to stop crying and didn’t intend to hurt or kill him, the affidavit said.