Kyota Hattori, a 24-year-old man who went out on Halloween, Sunday night, attacked and injured 17 people on a Tokyo train line with a knife, dressed as Joker from the Batman franchise.

Video of the incident was captured by Japanese train passengers and shared on Twitter, showing people squeezing through the train doors at the station in an attempt to flee. Another video showed what is suspected to be Kyota Hattori, wearing a purple suit and a green dress shirt, seated in the now-empty train car smoking a cigarette. A later clip showed him surrounded by police.

As officers scrambled to figure out what happened, Kyota Hattori allegedly told police that he adored the Batman villain and had been planning the attack for a long time.

According to authorities, the 24-year-old’s motive for the assault was that he “wanted to kill people and be given the death penalty.”

“I thought that if I killed two or more people, I would get the death penalty,” he told officers. “It didn’t matter who they were.”

He had been “thinking from around June of being sentenced to death,” he told authorities Monday morning, and he deliberately chose the limited express Tokyo train line heading towards the center of the city because he knew it would be the most crowded train.

Brandishing a knife and starting a fire on the train, 17 people were injured but all are expected to make full recoveries. One unnamed man in his 70s is said to be in critical condition about being stabbed in the chest.

“With a knife he was carrying, the man stabbed the right side of the chest of a male passenger in his 70s sitting in the train, but couldn’t achieve his aim (of murder),” a Tokyo police spokesman told reporters.

Authorities also revealed that Kyota Hattori told them that he “expressed regret” for not being able to kill anyone in the Tokyo train line attack.

Police found lighter fluid and a large, 12-inch knife after arresting the suspect. The train company also put out a brief statement stating that the driver was unaware of the what was happening on the train.

“First I thought it was something like a Halloween event,” one of the train’s passengers told FMT, “but I rushed away as a man carrying a long knife came in. I was very fortunate not to be injured.”

Another witness at the train station also initially thought the attack was “a Halloween stunt,” before they “saw a man walking this way, slowly waving a long knife.”

Another unnamed female passenger told reporters that Kyota Hattori was “committing this act without showing any emotion, just mechanically,” which she thought “brought fear to everyone” on board.

Speaking with Kyodo News, people close to Kyota Hattori who grew up with him in schools in Fukuoka Prefecture, southwestern Japan, said that he was “quiet” and such an attack was beyond his character.

One hometown man described him as someone who “wasn’t the type of person who would take the initiative,” but that he didn’t make many friends growing up.

Koyo Hattori allegedly told police that he was failing at work and was struggling in his relationships, as well.

On Monday morning, train passengers told Kyodo News that they were scared to ride the train after Sunday night’s events.

“I am terrified that I could get caught up in such an incident at any moment,” said an unnamed 58-year-old passenger. Another woman, 25, said that she usually listens to music on the train with earphones but didn’t this morning to stay vigilant.

Japan’s government condemned the attack on Monday, calling it “atrocious and brutal.”