TOKYO—The timing was coincidental, but the crime was more gruesome than the most grotesque ghouls and ghosts one can imagine. On Tuesday—Halloween—the Tokyo Metropolitan Police Department arrested a 27-year-old man on charges of desecration of a corpse after finding several severed human heads and body parts in and around his apartment. They are also investigating him on murder charges.

At least one of the heads was found in a cooler outside the front door of the flat, others were recovered from seven more coolers inside. Altogether, there were nine heads: eight female and one male, plus other bits and pieces of corpses. The flesh had been cut off and discarded, however, making identification difficult.

The suspect is Takahiro Shiraishi, an unemployed male living in an apartment building in Zama City, which is part of Tokyo. On Oct. 23, the police received a missing person report from the family of a 23-year old woman. Detectives discovered security camera footage of the woman and Shiraishi walking together. They were at a train station roughly 600 meters from his apartment.

After tracking him down, they discovered the bodies—it's not entirely clear if the missing woman was among them—and arrested him on the spot. While the Japanese police are often the subject of criticism, unless they face political interference they are often very good at their job.

According to the police, the woman had been contacted by Shiraishi via a social networking site, when she wrote that she was looking for someone to commit suicide with her.

Suicide bulletin boards became an issue in Japan years ago, but the proliferation of social networking sites has made it harder to track the discussions and forums of those wishing to kill themselves. Whether the woman who went missing last week was an assisted suicide or simply homicide also is unclear.

Japan makes a distinction between homicide and cases where the deceased asked to be killed. In the case of a college professor who strangled to death a student with whom he was having an affair, the court ruled that there was evidence the student wished to die. The professor was thus found guilty of “murder by contract” (shokutaku satsujin) and given a relatively light sentence of three and a half years of hard labor. According to the police, Shiraishi has already said that he strangled to death some of the victims for monetary gain.

“ In Japan, most murder investigations begin with an arrest for improper disposal of a corpse. ”

The police are researching missing persons reports to aid identification of the bodies. They are not yet sure the heads and body parts match, so a final tally of the dead is not conclusive.

There is still not much known about Shiraishi but Nikkan Gendai, an evening newspaper, is reporting that he worked as a scout recruiting talent to work in adult films or the sex industry in Kabukicho, Japan’s red light district. It is quite possible that some of his victims were spotted there.

Police sources confirmed that he had worked previously at one firm busted for violations of the anti-prostitution laws, but said that due to personal privacy issues they were not willing to discuss whether he had a criminal record.

In Japan, most murder investigations begin with an arrest for improper disposal of a corpse. The police and prosecutors then use the initial charges to hold suspects for the maximum of 23 days in confinement, take their time interrogating them, and typically rearrest them on murder charges after obtaining conclusive evidence that only the killer could know. The police term for the desired confession is bakuro no himitsu, which loosely translates as “the secret that exposes the crime.”

Neighbors reported to the police investigators at the scene on Tuesday that foul smells had been emanating from the apartment since late summer. One 33-year-old office worker living in the area told The Daily Beast, “In the last days of August, there was something awful smelling coming from that area, but I just thought it was garbage left out. It makes me nauseous to think about it now.”

The Japanese police are trying to narrow down the time frame in which the accused began dismembering the bodies. Most of the work reportedly was done in the bathroom using a saw. Shiraishi discarded the innards and flesh in the regular garbage. He reportedly put sand over the remains in the cooler boxes to diffuse the smell as if they were litter boxes.

Every year in Japan, thousands of people are reported missing, although roughly 70 percent are found within a week after a report is filed. The National Police Agency tally for 2016 was 84,850 people, and many cases are never reported at all. But it’s not often that on Halloween the police get nine leads on missing people all at once. For the enthusiastic and workaholic homicide detective, that’s likely to be a treat, of sorts.

UPDATE: Days after his arrest, Shiraishi reportedly confessed to cops that he had sought out suicidal people on Twitter to kill. He later told the press that he had committed the crimes for sex and money, and police said all eight female victims have been sexually assaulted. Prosecutors have charged him with nine counts of murder after five months of psychiatric examinations.