A former top bureaucrat of the farm ministry, who was arrested on the weekend over the murder of his son, has said the killing was prompted by the mass stabbing in Kawasaki near Tokyo last week, investigative sources said Monday.

Hideaki Kumazawa, 76, a former vice minister for agriculture, forestry and fisheries, has told investigators that he feared his son might harm children like the assailant in the Kawasaki knife rampage.

He heard his son, Eiichiro Kumazawa, 44, say he would "kill" students when he became angry at noise from an athletic meet at an elementary school near their house in Tokyo on Saturday, according to the sources.

Kumazawa called police after the incident that took place around 3:30 p.m. the same day, saying he had fatally stabbed his son. Eiichiro Kumazawa was found collapsed on a futon and confirmed dead after being taken to a hospital.

A former ambassador to the Czech Republic, Hideaki Kumazawa was arrested Saturday on suspicion of attempted murder and on Monday he was sent to prosecutors for alleged murder.

An autopsy found dozens of stab wounds and cuts on the son's body, the police said, adding the cause of death was bleeding from a wound to the neck.

Hideaki Kumazawa was quoted as saying his son "tended to be withdrawn from social life and exhibited violent behavior" toward him and his wife, the sources said. A note believed to have been written by the father was found at their home suggesting he intended to kill his son.

Ryuichi Iwasaki, the 51-year-old assailant in the knife rampage in Kawasaki on Tuesday, is said to have hardly left his home, where he lived with his uncle and aunt in their 80s.

Iwasaki allegedly attacked a group of Caritas Elementary School students and parents in the morning with 30-centimeter-long knives, killing two and injuring more than a dozen others before taking his own life.

According to the sources, Eiichiro Kumazawa had lived elsewhere in Tokyo for more than 10 years before returning to his parent's home in Tokyo's Nerima Ward in late May at his own request.

While he was living apart from his parents, he was seen having a quarrel about garbage with neighbors.

Hideaki Kumazawa also told investigators that he felt his life was in danger, prompting the police to suspect there was a long-standing feud within the family, the sources said.

He joined the predecessor of the farm ministry in 1967 and became vice minister in 2001.

He stepped down the following year amid criticism over the ministry's handling of a mad cow disease outbreak. He served as Japan's ambassador to the Czech Republic from 2005 to 2008.

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