The man told police that he set the fire because he thought "(Kyoto Animation) stole novels," according to Japanese media. It was unclear if he had contacted the studio earlier.
Police found surveillance footage from a nearby gas station showing Aoba filling containers with gas shortly before the attack, BBC News reported.
Update 8:45 a.m. EDT July 18: A Japanese fire official said 33 people are believed to have died in a fire at an animation studio Thursday, according to The Associated Press.
Authorities told NHK World-Japan that 36 other people were injured in the attack.
Original report: Almost 30 people are believed to be dead and dozens injured after a man set fire to a well-known Kyoto animation studio Thursday, authorities said.
According to the Mainichi, the man, whose name has not been released but is believed to be in his 40s, poured a flammable liquid and started the blaze at Kyoto Animation about 10:30 a.m. local time. At least 70 people were inside, but most were able to get out of the building, The Associated Press reported.
Officials said 20 people are confirmed dead and almost 10 believed to be dead, the AP reported. At least 35 people were hurt, with some in critical condition, authorities said.
The suspect was hospitalized for injuries, as well, officials told the Mainichi.
The studio has produced popular shows such as "Lucky Star," "K-On!" and "Sound! Euphonium."
The Associated Press contributed to this report.