The killing took place in the suspect's apartment in Sasebo, Nagasaki Prefecture, where Matsuo was beaten with a metal tool, strangled to death, and then partially dismembered and decapitated.
[1][2][3][4][5][6][7][8][excessive citations] The suspect, who was 15 at the time of the crime, but turned 16 shortly after, allegedly posted details and photos of the crime to the popular Japanese message board 2channel,[1] and told police that, "I wanted to kill someone.
[5][9][10][11][12][13][14][excessive citations] The suspect had previously attacked her father with a metal baseball bat, prompting him and her step-mother (her biological mother died the previous year) to move her into her own apartment when she began attending high school.
[17][18] The girl's 54-year-old father apologized to Matsuo's family in July 2014 about his daughter's mental health.
[19][20][21] In 2014, it was revealed that a psychiatrist who examined the girl had contacted a child consultation center in Nagasaki to reportedly warn officials that "If she is left as she is, she could kill someone.