Japanese police suspect that smoke from a fire filled a Kyoto Animation studio so quickly that many people suffocated before they could reach a door to its rooftop.
Police say the suspect poured what appeared to be gasoline on the first floor of the building in Kyoto City on Thursday, then set it ablaze. The suspected arson left 34 people dead and the same number of others injured.
The studio had a regular staircase and a spiral stairway. Police say 19 of the dead were found lying on top of one another in a section of the regular staircase leading from the third floor to the roof.
Police say they discovered the door to the roof at the top of the staircase remained closed, although it could have been opened from the inside without a key at the time of the blaze.
Police suspect that most of the victims died of smoke inhalation and carbon monoxide poisoning.
A studio employee who was on the second floor of the building told NHK that black smoke billowed from the spiral stairway less than 15 seconds after he heard the sounds of people arguing coming from the first floor.
The suspected arsonist, Shinji Aoba, is receiving treatment for serious burns at a hospital in Osaka. When he recovers sufficiently, police plan to arrest the 41-year-old on suspicion of arson and murder.