Man behind deadly Taiwan metro attack planned it for over a year

Three police officers stand in a cordoned off street with one pointing a light at the camera

Police quickly cordoned off the scene following the attack in central Taipei. (AP Photo: Chiang Ying-ying)

In short:

Investigators say the man suspected of attacking innocent bystanders in Taipei had planned the assault for more than a year.

Chang Wen purchased weapons including grenades and gas canisters in the year leading up to Friday's attack.

What's next?

Police are still probing Wen's motives.