A hearse carrying the coffin of Japanese schoolgirl Aiwa Matsuo, allegedly murdered by a classmate, leaves a funeral hall in Sasebo, Japan. (Jiji Press/AFP/Getty Images)

The 16-year-old girl has lived alone since April. Police said her mother had died. And her father had married another woman soon after. And so, when the girl invited a teenager named Aiwa Matsuo to her apartment in Nagasaki, Japan, on Saturday, they had the place to themselves.

“I told her that I wanted to see her and asked her to come,” the girl later explained to investigators, according to the Japan Times. She harbored no animosity toward 15-year-old Aiwa, who attended the same high school in Sasebo in southwest Japan. Nonetheless, she told police that after the two went shopping that afternoon, “I came home with her so I could kill her.”

According to Agence France-Presse, she reportedly told police she “wanted to kill someone” and “wanted to dissect a dead body. … I bought the tools by myself.”

Around 8 p.m. that night, five hours after Matsuo left her home, police said the girl, whose name is being withheld because she is a minor, bludgeoned her classmate. She allegedly strangled her to death with a rope and then, police said, brandished her “tools.”

Later that night after 10 p.m., several macabre messages appeared on the popular 2Channel Internet forum. There were seven gruesome pictures, including a bloody cloth and a series of pictures of bloody hands.

A high school student in Japan was arrested on suspicion of killing her classmate. (Reuters)

And there was a message, according to the Japan Times, with the subject: “I have ended up killing.”

“Oh no,” it said, “blood keeps pouring out even though even thought I have wiped it away many times.” Another said: “I’ve tried to warm [the body] as it got cold, but it doesn’t warm up … Everyone, [do you want to know] what color the brain is? … I’ll take good care of the brain and the spinal cord, putting them in a solution.”

What police found the next day on a bed inside the apartment was horrifying. The victim was found decapitated, with her left hand chopped off, investigators told news organizations. Her abdomen had been slit open. Police found a hammer nearby. The police allege the girl had been “using tools … and something like a cord.”

Were the images on the Internet from the scene of this crime? Police are still trying to figure that out.

In interviews with police after the discovery, the girl allegedly confessed to the grisly murder that shook the nation.

Little by little, a few more details about the suspect, who was reportedly planning to study abroad, have emerged. AFP said she went to school for just three days in the first semester of this year and a teacher from her junior high school checked on her weekly.

Meanwhile, the victim’s funeral was on Tuesday — an event attended by several hundred people, according to the Japan Times. “She was a cute one,” one woman who said she knew Matsuo told the newspaper. “I can’t take what happened. I just hope I can do something for her dejected parents.”