Hideaki Kumazawa is sent to prosecutors from the Nerima Police Station in Tokyo on June 3. (Nobufumi Yamada)

A former top bureaucrat of the agriculture ministry said he had no choice but to kill his violent son to prevent another stabbing rampage against schoolchildren, according to investigative sources.

The murder case against Hideaki Kumazawa, 76, who was administrative vice minister of agriculture, forestry and fisheries from 2001 to 2002, was sent to prosecutors on June 3.

He is accused of fatally stabbing his unemployed son, Eiichiro, 44, at their home in Tokyo on June 1.

Kumazawa, who also served as ambassador to the Czech Republic from 2005 to 2008, told investigators that “I had to prevent my eldest son from killing or injuring children,” the sources said.

Kumazawa referred to the May 28 stabbing spree in Kawasaki that killed a Foreign Ministry diplomat and an 11-year-old girl, and injured 18 others, most of whom were elementary school children.

The 51-year-old suspect who killed himself after that attack was described as a recluse.

“My son tended to confine himself at home. He sometimes committed violent acts against me and my wife,” Kumazawa, who lives in Nerima Ward, was quoted by the Metropolitan Police Department as saying. “His violence had continued from his junior high school days.”

On the morning of June 1, Eiichiro apparently became irritated by a sports festival held at a nearby elementary school.

According to the father, Eiichiro complained: “The sounds of the elementary school’s athletic meet are noisy.”

Kumazawa said he warned his son not to say such a thing, which caused Eiichiro to lose his temper.

“I thought that I had to prevent him from turning his anger against the children,” police quoted Kumazawa as saying.

According to police, Kumazawa stabbed Eiichiro in the chest and other parts of the body several times with a kitchen knife around 3:30 p.m. that day.

Ten minutes later, the father phoned police, who arrived at the house and found the son on his back on a “futon” mattress in a Japanese-style room on the first floor.

Police arrested Kumazawa on suspicion of attempted murder. After the son died at a hospital, police changed the suspicion to murder.

A memo written by Kumazawa was found in the home, saying, “There is no other way except to kill him.”

Kumazawa had been living with his wife and son in the house. His wife was not at home when the son was stabbed.

Residents living nearby said they did not know that the couple had a son.

“The Kumazawas moved here about 10 years ago,” an 86-year-old neighbor said. “I never saw anyone who appeared to be their son.”

Eiichiro started living with his parents at the house in May.