【明報專訊】On 8th June 2008, in the Akihabara (秋葉原) shopping quarter, Tokyo, Japan, a 25-year-old man called Tomohiro Katō (加藤智大) crashed a car into a crowd before stabbing passers-by with a dagger. Seven people were killed, and ten others injured.

■What were the motives behind the attack?

It is believed that Katō's unhappy childhood and the frustrations he had experienced as an adult impelled him into carrying out the attack.

Katō grew up in a suburban home in Aomori, Honshu (本州青森市). He had a middle-class upbringing, his father being a top manager at a financial institution. However, as Katō's brother revealed, their parents had put immense pressure on them to excel in their studies.

Katō did excel in elementary school. However, he did not get along with his classmates in the elite high school he went to. It was then that he began to act violently.

At the time of the attacked, Katō worked at an auto parts factory in central Shizuoka Prefecture (靜岡縣). Three days before the attack, Katō accused his colleagues of hiding his uniform. He left work immediately afterwards, thinking he was going to lose his job. Before the attack, he allegedly posted messages on the Internet, saying, "I will kill people in Akihabara."

■Why have there been so many ''copycat'' killings since?

A number of killings, in which people have killed others whom they do not know, have happened since the Akihabara attack. On 21 May 2014 Cheng Chieh (鄭捷), who was then 21, went on a killing spree on a Taipei Metro (台北捷運) train near Jiangzicui Station (江子翠站). He killed four people and injured twenty-two others. On March 28 this year in Taipei, a 33-year-old man murdered a four-year-old. He was a total stranger to the victim's family.

All these incidents are thought to have been "inspired" by the Akihabara killing. As such, they are all regarded as "copycat crimes (模仿罪行)" - criminal acts modelled on or inspired by a crime that has been reported in the media or described in fiction. One reason why they happen is that perpetrators who feel ignored by society hanker after the kind of media coverage a previous crime has attracted. Indeed, Cheng Chieh once told his old classmate he wanted to kill people "in the Akihabara style". Furthermore, in the few days after Taipei Metro massacre, there were multiple instants in which people said on the Internet they wanted to kill people the way Cheng did.

■What can be done to prevent such crimes?

Many have proposed tougher punishments - including capital punishment (死刑) - as a solution. However, capital punishment has not been abolished in Taiwan or Japan. In fact, Cheng Chieh was executed last month. Some argue that criminals like Cheng are simply too eager to get society's attention to fear death. They think capital punishment encourages rather than deters violence.

Some believe such crimes show the mental healthcare system is inadequate, arguing that more resources should be devoted to spotting individuals who have a tendency to commit such crimes. Others, quoting the Italian criminologist Cesare Lombroso (龍勃羅梭), say it is the genes that make a person a criminal and there is little we can do to prevent such crimes.