TOKYO — Moments after a lighter was put to a pool of gas at a renowned anime studio in Kyoto, Japan, igniting an explosive fire that killed 34 people, Shinji Aoba tried to run away from the scene.

Mr. Aoba, who has been named a suspect in the alleged arson, did not get far, as he was badly burned himself. Chased down by studio workers, he fell to the ground, and several witnesses captured the scene on their cellphones. The police swarmed around him as he lay on his back on the street, his knees bent.

“I did it because they stole my novel,” he said, according to police officials cited by NHK, the public broadcaster. According to a bystander quoted by NHK, Mr. Aoba warned police officers not to touch him when they asked if he could stand.

“They plagiarized my work,” he said. “Call the president. I have something to tell him.”

The picture emerging of Mr. Aoba was of an unstable 41-year-old with a troubled past. Police sources cited by NHK said he had served prison time for robbery and was being treated for an unspecified mental illness. Mr. Aoba has not yet been officially arrested because police officials said his medical needs are too critical.

On Saturday, Mr. Aoba was transferred from a hospital in Kyoto to a university-based center in Osaka that has a specialized burn unit. Video footage on NHK showed him on a stretcher, both legs swathed in white bandages, before hospital workers covered him with a pale blue sheet as they loaded him onto a helicopter.

The nation was shocked by the blaze at the studio, Kyoto Animation, which appeared to be the worst mass killing in Japan in decades. The victims have not yet been identified publicly; according to the Kyoto Police, some of the bodies are burned so badly that they are difficult to identify.