Taipei, Taiwan: The organiser of a party which saw a fireball rip through a crowd in a Taiwan waterpark leaving 15 dead was found guilty of negligence on Tuesday and jailed for four years and 10 months.

Lu Chung-chi, owner of Colour Play Asia, was behind the event at Formosa Fun Coast where coloured corn starch being sprayed on partygoers ignited under the heat of stage lights last June, sending them running for their lives and leaving hundreds injured.

He was found guilty of negligence causing death at Taipei’s Shihlin district court as relatives of the victims gathered outside waving banners calling for justice.

Judge Kuo Hui-ling read the verdict with no further comment—Lu was not in court.

The case has angered grieving relatives and the families of the injured as only Lu was indicted over the disaster—he was one of nine people investigated, including the chairman and president of the water park.

Campaigners have urged prosecutors to open a new investigation into the accident.

The high prosecutors’ office told AFP Tuesday it has ordered a district court to reopen the investigation into the other eight originally investigated.

Almost 500 partygoers were injured in the blast, more than 200 of them seriously. Horrific video footage showed revellers—most of them between 18 and 25-years-old—screaming as they tried to escape.

Some were left with more than 90 percent burns.

An investigation showed the hottest parts of the stage lights hit temperatures of more than 1,000 degrees Celsius, while the powder’s ignition point was just 500 degrees Celsius.