The suspect in the murder of his Shinto priest sister at a Tokyo shrine last week sent about 2,800 letters insulting the victim to shrines across Japan, investigative sources said Friday.

Police suspect Shigenaga Tomioka, 56, held a fierce grudge against his 58-year-old sister Nagako for her ascension to the chief priest post at the Tomioka Hachimangu shrine. The letters demanded she be expelled from the shrine, the sources said.

Investigators believe Shigenaga murdered Nagako with a samurai sword and that his wife Mariko, 49, slashed the driver of the shrine's car before Shigenaga killed his wife and then himself on the night of Dec. 7.