A 17-year-old boy from Saga Prefecture who hijacked an intercity bus from Saga to Hiroshima last week sent a message to the National Police Agency in March in which he said he would "start a revolution," police sources said Saturday.
The sources said the boy -- now under arrest in Hiroshima -- also told police detectives investigating the case that he sent letters to the Education Ministry, the Prime Minister's Official Residence and NHK, but said, he didn't remember the contents.
Police sources said the message to the NPA was mailed out in early March, just before he was hospitalized at a psychiatric facility in Saga.
The NPA took no action as officials were unsure of the meaning of the letter, in which the boy referred to himself as "God" and made other incoherent references, police sources said.
The suspect, who stabbed a female passenger to death during the hijacking, commandeered the Fukuoka-bound bus after he was temporarily released from the state-run rehabilitation facility in Saga.
According to previous police accounts, the boy sent e-mail messages to government offices in Tokyo's Kasumigaseki district on March 4 saying, "I will attack Kasumigaseki."
Before the boy was institutionalized, his parents consulted police saying he was locking himself up inside his room for long periods of time and behaving irrationally.
Police said they found an assortment of knives in the boy's room as well as a note saying, "Another person in me" ordered him to kill.
On May 6, police also found an assortment of knives in the boy's room.
They also confiscated a personal computer from his room that contained records showing he had frequently accessed the Internet, the sources said.
The police are searching bulletin boards he accessed to determine whether he left any messages related to the hijacking, the sources said.