A 24-year-old man in a Batman Joker costume attacked passengers on a Tokyo train line last night, injuring 17 people.
The police arrested the alleged attacker at the scene.
A man believed to be over 60 years old was in critical condition after being stabbed with a knife, while witnesses said the attacker spilled liquid on the train and started a fire.
A video uploaded to Twitter showed a steady stream of people running away from a train car where seconds later a flame lit up.
Another video showed passengers hurrying to squeeze out of the windows of the train onto the platform on which the train had made an emergency stop.
“I thought it was a Halloween stunt,” a witness told the Yomiuri newspaper, remembering the moment when he saw other passengers panicked towards his car.
“Then I saw a man walking this way and slowly waving a long knife.”
The witness said there was blood on the knife.
Another video on Twitter showed a man in a purple suit and light green shirt, like the Joker wears, sitting on an empty train, panting on a cigarette, crossing his legs and looking calm.
In a subsequent clip he can be seen through the window as he is surrounded by the police.
The attack occurred around 8 p.m. local time on the Keio express line to Shinjuku, the busiest train station in the world.
The facility on the Keio Line was suspended until late at night.