A 20-year-old member of a yakuza syndicate, who was arrested in Tokyo on Wednesday over the death of his girlfriend’s 3-year-old son, is believed to have previously abused the boy, police said Thursday.

The Metropolitan Police Department sent the case to prosecutors the same day.

Naoya Nagatomi, a member of a group affiliated with major yakuza syndicate Sumiyoshi-kai, was arrested Wednesday for repeatedly hitting and kicking Ayato Arai on Monday.

An ambulance was called to an apartment in Ota Ward in the early hours of Wednesday — more than a day after the incident. When it arrived, the boy was covered with bruises and was not breathing.

He was later confirmed dead at a hospital, having suffered a subdural hematoma and hemorrhage in the back of his eyes.

Police will further investigate the case on suspicion that Nagatomi caused injury resulting in death.

Nagatomi, 195 cm tall and weighing 120 kg, admitted to the charges. “I did it because I was angry that (the boy) glared at me. I struck his face many times and threw him to the ground,” police quoted him as saying.

“He jabbed a cooking knife into the floor, and kicked using heel drops. He also said ‘die,’ ” the 22-year-old mother told police.

The mother also told police that Nagatomi had hit the boy before Monday’s incident. Nagatomi said he hit the boy “as a discipline,” according to police.

Nagatomi and the child’s mother have lived together since early January.

The mother told police that Nagatomi abused the boy for about 1½ hours at dinner on Monday. She tried to stop him, but Nagatomi was also violent toward her, according to her statement to police.

When she finally made the emergency call on Wednesday, she said the child had developed a fever and was not reacting to stimulus.

Ayato was found in cardiopulmonary arrest, and the hospital that confirmed his death reported the case to police.

The police also plan to investigate why it took so long for the mother to call for help.

According to Ota Ward and a Shinagawa child consultation center, no bruise or other sign of abuse was found on the boy’s body when he received a public health check-up for 3-year-olds last month, and no request for child care consultation or reports of abuse had been made prior.

KEYWORDS Yakuza, Abuse, arrest, boy