(Newser) – The man accused of setting fire to an anime studio in Japan, killing at least 33 people in one of the country's deadliest postwar mass murders, has been identified as Shinji Aoba. The 41-year-old man is being treated for burns in a hospital and police have so far been unable to question him, reports the BBC. His motive is unclear, though witnesses say they heard him complain that Kyoto Animation had plagiarized his novel before he splashed flammable liquid from a bucket and set it on fire. CCTV footage reportedly shows Aoba buying gas in containers from a nearby station before the attack. Kyoto Animation president Hideaki Hatti says the studio recently received threatening letters, though he doesn't know whether they were from the suspect.

Aoba would not have been able to enter the studio building if he had chosen a different day, the Asahi Shimbun reports. Hatti says people normally need ID cards to enter the building, but the system was temporarily deactivated Thursday because of a meeting involving outside guests. Experts say nature of the blaze and the construction of the building—which did not have sprinklers, and wasn't required to under Japan's fire code—may have contributed to the high number of deaths. They say a spiral staircase leading from the first to the third floors would have acted as a "chimney," causing fire and smoke to spread with terrifying speed. Nineteen bodies were found piled on top of each other on stairs between the third floor and roof; Kyodo reports the door was shut but could reportedly be opened from the roof side. Police say that out of 74 people in the building when the fire broke out, only six escaped uninjured. (Read more Japan stories.)

