Tomohiro Kato was responsible for one of the most horrifying mass murders in modern Japanese history.

Three people were killed when he drove a truck into a lunchtime crowd of pedestrians in the Akihabara shopping district at 25.

He used a dagger to stab bystanders, killing four and wounding eight.

Police captured him at the site and he later confessed to his actions in court, citing internet harassment as his motivation.

At the time, his crime provoked great discussion in Japanese culture regarding random killings, online influence, and inadequate mental health treatment for young people.

The Japanese media claimed on Tuesday that Kato was hung at the Tokyo Detention Center.

This is the nation's first execution of the year. Three people were executed by hanging in December, while more than 100 convicts remain on death row.

After Kato's murdering spree, knife possession laws were also strengthened.

In 2011, the Tokyo District Court sentenced him to death, stating that his terrible crime lacked "a shred of humanity."

His plea to commute his death sentence was denied in 2015.

Despite widespread opposition from international and local human rights organizations, Japan remains one of the few affluent nations that still employs the death penalty.