The father of the 16-year-old girl who was arrested in July in Sasebo, Nagasaki Prefecture, on suspicion of killing and dismembering a female classmate was found hanged Sunday in an apparent suicide, police said.
The 53-year-old man was found in his Sasebo home.
His death could make it even harder for investigators to determine the girl's motive for the grisly crime, sources familiar with the case said, noting that he had been cooperative.
The girl allegedly strangled her 15-year-old classmate to death on July 26 before mutilating the corpse at the suspect's apartment in Sasebo, where she lived alone. She was arrested the next day.
The teen started living alone earlier this year after her mother died from cancer last year. Her father remarried shortly afterward.
The girl began seeing a psychiatrist after seriously injuring her father with a metal baseball bat in March, a lawyer said.
She is currently in a medical facility undergoing psychological evaluation at the request of prosecutors.
The father had asked a school official not to reveal the beating, the Nagasaki prefectural board of education said in a report last month.
After the slaying, the father issued a statement apologizing to the victim's family. He said his daughter's act "can never be forgiven for any reason or cause."
In the statement, the father said he "was losing his confidence in his ability to continue living, as (the crime) cannot be compensated" even with his own life.
He also revealed through his lawyer that he had asked his daughter's psychiatrist to have her hospitalized the day before the killing after she confided to her stepmother that she "wanted to kill someone," and that his request was rejected.