A knife-wielding university student in Taiwan today went on a stabbing spree aboard a subway train, killing four people and injuring at least 21 others, police said.

The 21-year-old student named Cheng Chieh was arrested after the incident. Police said that this was the first incident in the subway system of the city.

The police said that at least half of the injured were in a serious condition. Three people died at the station only while a 62-year-old victim succumbed to her injuries in hospital.

The stabbing spree happened around 0800 GMT when Cheng started attacking travellers on a subway train.
Cheng revealed his motives behind the attack during police questioning. "He told the police that he had wanted to do a 'big thing' such as this since his childhood," Chen Kuo-en, chief of the New Taipei City police bureau, told reporters.

"He said he had planned to do this after his graduation, but last week decided to act ahead of his schedule," Chen said, adding that the attacker did not show any medical record of mental disorder.
Cheng carried two knives, including a 30-centimetre (12-inch) long knife and a smaller one, which he had bought from a supermarket in Taipei.

"He started his attack from the last carriage of the train," a woman told cable news network TVBS.
Another passenger said: "I was terrified when I saw an elderly man covered with lots of blood walking out of a carriage when the train arrived at the Chiangzitsui station and."