Seventeen people were injured in a knife and arson attack on a train in Tokyo on Sunday night, according to the police.
The local media reported on Monday that the arrested suspect told investigators that he adored Batman’s villain character, the Joker, and that was why he wore the costume.
Kyota Hattori, 24 years old, arrested at the scene on suspicion of attempted murder on Sunday night, was also quoted as saying that he “wanted to kill people and be given the death penalty.”
The suspect said that he had been thinking of being sentenced to death since June.
Photos and videos posted on social media from the scene showed Mr. Hattori wearing a Joker-like costume with a green shirt and purple suit.
He told the police he chose a limited express train bound for the city center with few stops because passengers are generally crowded.
The suspect even expressed regret at failing to kill anyone in the attack.
The police said that Mr. Hattori visited Tokyo’s Shibuya district, a hot spot for costumed party-goers to celebrate Halloween about two hours before the incident.
Among the injured, a man in his 70s was seriously hurt after allegedly being stabbed by Mr. Hattori in the chest.
The other 16 victims aged between their teens to their 60s sustained minor injuries, including smoke inhalation.
Mr. Hattori also allegedly set a fire on the train using lighter fluid, burning part of the fifth carriage.
The incident took place on a 10-car train bound for Shinjuku in central Tokyo and caused panic among passengers who scrambled to escape through train windows.
After the incident, the train stopped at a station that was not originally planned for the fast train, but the doors did not open immediately.
The train operator, Keio Corp, said as the train did not stop at the right position, the staff were unaware of what had happened at that time.
They decided not to open doors to prevent passengers from falling through a gap between the train and the platform.
Police found a knife, several plastic bottles which possibly contained lighter fluid, and an aerosol can in a train car.
After the incident, the transport ministry asked all the railway companies in Japan to strengthen vigilance to ensure safety.
Several attacks on trains and station premises in the Tokyo area have occurred recently.
A man stabbed and slashed 10 passengers in August on an Odakyu Electric Railway commuter train.
Two men were stabbed on October 15 by a man at JR Ueno Station.
In a separate incident, two people were injured in a Tokyo subway station in late August as a man sprayed sulfuric acid at the face of another man.