The men who fatally stabbed a 51-year-old housewife in Haguro, Yamagata Prefecture, on Saturday did not use a knife from the premises, indicating the perpetrators were prepared to kill, sources close to the investigation said Monday.
Kayoko Sato was stabbed in the front entrance to her house after being bound with electrical cord. An autopsy conducted Sunday showed she died of blood loss after the weapon entered her heart.
A search of the house showed that no knives or other objects that could have inflicted the wound were missing, leading police to think the men were armed before they broke in, the sources said.
The Satos are well known in the neighborhood because of their extensive roots there and substantial real estate holdings. About 25 years ago, more than 20 Japanese swords were stolen from the Sato's storehouse, and investigators are not ruling out the possibility that the men broke into the house in the hope of stealing old works of art, according to the sources.
Investigators said Sato's eldest daughter, Atsuko, 16, heard her mother scream and ran to the entrance to see the woman surrounded by three men. Atsuko herself was captured by a fourth man who bound much of her body with masking tape, police said. The girl sustained minor injuries.
Police said that several footprints not made by family members were found in the entrance, and sources said investigators suspect the men stabbed Kayoko because she resisted.
According to police, witnesses have said they saw three men in a station wagon parked in the road leading up to Sato's home a day before the incident.
Sato's husband, Akira, 52, was in hospital at the time, and his two other children were out.