sorrow floats

Tuesday marked the one-year anniversary of a train derailment that killed over 100 people in western Japan.

The train derailment killed 107 people and injured 555 others on April 25, after a West Japan Railway train on the Fukuchiyama Line derailed and slammed into an apartment building in Amagasaki.

The family of victims are still deep in sorrow.
Why did this happen?