A knife-wielding attacker went on a stabbing spree aboard a Taipei subway train Wednesday, killing four people and wounding 21 others, police said.
Cheng Chieh, a 21-year-old college student, was immediately arrested after the incident, the first fatal attack on the city's subway system since it began operations in 1996, police said.
The police, who had earlier put the number of injured at 25, said 22 travellers were wounded and hospitalised. Half of the wounded were in a serious condition, they said.
Three people were initially reported to have died in the attack and a fourth victim, a 62-year-old woman, died later in hospital. The other three victims were a woman and two men.
The stabbing spree happened around 0800 GMT when the student, wearing a red T-shirt, began attacking travellers on a subway train outside Taipei, sending hundreds of people screaming and fleeing for help.
When the train pulled into the next station, Cheng fled and was chased by police before being kicked to the ground by a passenger and overwhelmed by security officials.
Cheng spoke of his motives 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 had no medical record of mental disorder.
The student bought two knives, including a 30-centimetre (12-inch) long knife and a smaller one at a supermarket in Taipei in preparation for the attack, Chen said.
Television images showed pools of blood in the train and passengers who survived the stabbings giving witness accounts.
"He started his attack from the last carriage of the train," a woman said as she gave her tearful account in an interview with the 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."
After being alerted to the attacks, authorities immediately reinforced police deployment on the busy subway system, which transports around 1.85 million visitors per day.