Lu Chung-chi, the man responsible for organising a waterpark party that ended in a fatal explosion killing 15 people, has been jailed for four years and 10 months.

Receiving his sentence in court in Shilin, Taipei, Lu was found guilty of negligence. He did not attend the verdict. Some victims and their relatives have been telling the local press that the sentence is not long enough.

More than 500 people were injured and 15 people died when a starch-based powder ignited during a Color Play Asia event at the Formosa waterpark in New Taipei City, Taiwan, on 27 June 2015. The flames engulfed a large portion of the dance area almost instantaneously.

“Most of the victims were very young and their wonderful lives were about to start. They had beautiful dreams to be realised,” said a press statement provided by the court. “Because of the explosion, 15 of them lost their lives and most of the survivors suffer tremendous physical and emotional pain and torment.”

“Relatives of the deceased suddenly lost their family members and suffered irreparable and excruciating pain and regret,” it said. “The explosion happened due to the negligence of the defendant.”

Lu was arrested soon after the incident and charged in October on multiple charges including negligent homicide.