Sunday¡¯s stabbing rampage on a Tokyo train by a man dressed up as the Joker from the ¡°Batman¡± franchise was a sobering reminder of how vulnerable trains and subways are to violent, indiscriminate attacks in a metropolis heavily reliant on public transportation.

The incident, in which the assailant brandished what appeared to be a kitchen knife and set fire to cars on a Keio Line train on Halloween night, left 17 passengers injured. One of them, a man in his 70s, was in critical condition after reportedly being stabbed in the chest. After assaulting the man, the assailant, identified as 24-year-old Kyota Hattori, went on to scatter flammable fluid and burn a seat, causing the train to fill with smoke.

Hattori was arrested at the scene for attempted murder. He later told investigators that his motive was to ¡°sentence himself to death¡± by killing two or more people.