The man suspected of starting a fire that killed 33 people at a Japanese animation studio believed it had stolen his idea for a novel, according to local media.

According to investigative sources, the suspect said he set the Kyoto Animation Company building on fire because it “stole a novel”.

The person thought to be behind the attack was identified as Shinji Aoba by Japan’s public broadcaster NHK on Friday.

At about 10.30am local time on Thursday, a man reportedly shouting “die” burst into the three-storey studio before dousing the entrance with what appeared to be petrol and setting it ablaze.

The explosive blaze killed 33 people and 10 more were in a critical condition late on Thursday, according to officials.

Kyoto fire: 33 dead in suspected arson attack at animation studio Show all 16 1 /16 Kyoto fire: 33 dead in suspected arson attack at animation studio Kyoto fire: 33 dead in suspected arson attack at animation studio A woman leaves flowers for the victims of a suspected arson attack at the Kyoto Animation Company studio building in Kyoto, Japan, which claimed 33 lives on 18 July 2019. AP Kyoto fire: 33 dead in suspected arson attack at animation studio A woman sheds tears as she visits a makeshift memorial honoring the victims of Thursday's fire at the Kyoto Animation Studio building, background center, Friday, July 19, 2019, in Kyoto, Japan. A man screaming "You die!" burst into the animation studio in Kyoto, doused it with a flammable liquid and set it on fire Thursday, killing dozens of people in the attack that shocked the country and brought an outpouring of grief from anime fans. (AP Photo/Jae C. Hong) Jae C. Hong AP Kyoto fire: 33 dead in suspected arson attack at animation studio A fan of Kyoto Animation cries as she visits the area near the studios' building which was torched by arson attack, in Kyoto, Japan, July 19, 2019. REUTERS/Kim Kyung-Hoon KIM KYUNG-HOON REUTERS Kyoto fire: 33 dead in suspected arson attack at animation studio Residents pray for victims of a fire which hit the Kyoto Animation company studio the day before, killing 33 people, in Kyoto on July 19, 2019. - Japanese police are investigating a suspected arson that killed 33 people in one of the country's deadliest apparent crimes in decades, with the motive for the blaze still unclear. (Photo by JIJI PRESS / JIJI PRESS / AFP) / Japan OUTJIJI PRESS/AFP/Getty Images JIJI PRESS AFP/Getty Images Kyoto fire: 33 dead in suspected arson attack at animation studio Police officers move towards the Kyoto Animation company studio wwhich was set on fire killing at least two dozen people in Kyoto on July 19, 2019. - A suspected arson attack at an animation production company in Japan killed 33 people and injured dozens more, after a man reportedly doused the building with flammable liquid and shouted "drop dead." JAPAN OUT (Photo by JIJI PRESS / JIJI PRESS / AFP) / Japan OUTJIJI PRESS/AFP/Getty Images JIJI PRESS AFP/Getty Images Kyoto fire: 33 dead in suspected arson attack at animation studio Firefighters work as smoke billows from a three-story building of Kyoto Animation in a fire in Kyoto, western Japan, Thursday, July 18, 2019. Kyoto prefectural police said the fire broke out Thursday morning after a man burst into it and spread unidentified liquid and put fire. (Kyodo News via AP) AP Kyoto fire: 33 dead in suspected arson attack at animation studio Firefighters work at the Kyoto Animation building which was torched by arson attack, in Kyoto, Japan, July 19, 2019. REUTERS/Kim Kyung-Hoon KIM KYUNG-HOON REUTERS Kyoto fire: 33 dead in suspected arson attack at animation studio KYOTO, JAPAN - JULY 19: A police officer stands guard next to the Kyoto Animation Co studio building after an arson attack, on July 19, 2019 in Kyoto, Japan. Thirty three people are believed dead and dozens injured after a suspected arson attack on the animation studio. Police were quoted by local media as saying a 41 year-old man broke into the Kyoto Animation Co studio on Thursday morning and sprayed petrol before igniting it. Japan's Prime Minister Shinzo Abe described the incident as 'too appalling for words'. (Photo by Carl Court/Getty Images) Carl Court Getty Images Kyoto fire: 33 dead in suspected arson attack at animation studio Two men pay respects at a makeshift memorial site to honor the victims of Thursday's fire at the Kyoto Animation Studio building, background center, Friday, July 19, 2019, in Kyoto, Japan. A man screaming "You die!" burst into the animation studio in Kyoto, doused it with a flammable liquid and set it on fire Thursday, killing dozens of people in the attack that shocked the country and brought an outpouring of grief from anime fans. (AP Photo/Jae C. Hong) Jae C. Hong AP Kyoto fire: 33 dead in suspected arson attack at animation studio TOPSHOT - A firefighter investigates inside the building where over 30 people died in a fire at an animation company building in Kyoto on July 19, 2019. - A suspected arson attack at an animation production company in Japan killed 33 people and injured dozens more, after a man reportedly doused the building with flammable liquid and shouted "drop dead". (Photo by Buddhika Weerasinghe / AFP)BUDDHIKA WEERASINGHE/AFP/Getty Images BUDDHIKA WEERASINGHE AFP/Getty Images Kyoto fire: 33 dead in suspected arson attack at animation studio Firefighters battle a fire at Kyoto Animation Company studio in Japan 18 July 2019. Police and fire officials believe the fire was started by a man who poured an 'unidentified liquid' around the building. Kyodo/via Reuters Kyoto fire: 33 dead in suspected arson attack at animation studio Smoke billows from a fire at the Kyoto Animation studio in Kyoto, Japan July 18, 2019, in this still image obtained from a social media video. INSTAGRAM / @XRAY_RAIX via REUTERS. ATTENTION EDITORS - THIS IMAGE HAS BEEN SUPPLIED BY A THIRD PARTY. MANDATORY CREDIT "INSTAGRAM / @XRAY_RAIX" NO RESALES. NO ARCHIVES. SOCIAL MEDIA Instagram/@xray_raix via Reuters Kyoto fire: 33 dead in suspected arson attack at animation studio People walk past images of anime characters in the Akihabara district in Tokyo on July 19, 2019. - The devastating apparent arson attack on a well-respected Japanese animation firm Kyoto Animation in Kyoto on July 18 which killed at least 33 people has left anime fans and industry insiders alike "heartbroken", with many likening the fire to a "terrorist attack." (Photo by Behrouz MEHRI / AFP) / TO GO WITH Japan-fire-animation-anime,FOCUS by Karyn NISHIMURABEHROUZ MEHRI/AFP/Getty Images BEHROUZ MEHRI AFP/Getty Images Kyoto fire: 33 dead in suspected arson attack at animation studio Firefighters battle a fire at the Kyoto Animation Company studio building in Japan on 18 July 2019. Kyodo/via Reuters Kyoto fire: 33 dead in suspected arson attack at animation studio A fire fighter watches an animation company which caught fire in Kyoto on July 18, 2019. - A fire at an animation company in Japan's Kyoto on July 18 killed one person and injured dozens more, several of them seriously, a fire department spokesman said. (Photo by JIJI PRESS / JIJI PRESS / AFP) / Japan OUTJIJI PRESS/AFP/Getty Images JIJI PRESS JIJI Press/AFP/Getty Images Kyoto fire: 33 dead in suspected arson attack at animation studio Overview of an animation company building which caught fire in Kyoto on July 18, 2019. - A fire at an animation company in Japan's Kyoto on July 18 killed one person and injured dozens more, several of them seriously, a fire department spokesman said. (Photo by JIJI PRESS / JIJI PRESS / AFP) / Japan OUTJIJI PRESS/AFP/Getty Images JIJI PRESS JIJI Press/AFP/Getty Images

There were 74 people inside the building when the fire started. None of the victims’ identities have yet been disclosed.

It marks the country’s worst mass killing since a suspected arson attack in Tokyo killed 44 people in 2001.

The suspected attacker, thought to be from the Tokyo suburb of Saitama, 300 miles east of Kyoto, is believed to have bought two 20-litre fuel cans and prepared the petrol in a park near the studio, Nippon TV said, citing police.

The broadcaster said the man, who was taken to hospital, was under anaesthesia after burning himself and police were unable to question him.

A woman who witnessed the suspect being detained told reporters he “seemed to be discontented, he seemed to get angry, shouting something about how he had been plagiarised”.

On Friday, a Kyoto Fire Department official said the Kyoto Animation building did not have any sprinklers or indoor hydrants installed since they were not legally required by the fire code.

The official said that, since it was classified as an “office”, the building was not required to have such equipment.

An October inspection of the building found that fire extinguishers and emergency alarms were installed as required.

A woman prays at a makeshift memorial for victims of a suspected arson attack at the Kyoto Animation Company studio building, in Kyoto, Japan, 19 July 2019 (AP)

Anime fans gathered at the edge of the police cordon surrounding the charred building on Friday to lay flowers and offer prayers for the victims of the attack.

Fighting back tears as he lay flowers in the rain, 71-year-old Kozo Tsujii said: “I imagine many of the people who died were in their 20s.

“I’m just very, very sad that these people who are so much younger than me passed away so prematurely.”

Anime fan Yuichi Kumami, 27, who had taken time off work to lay flowers at the site, said: “It’s hard to put into words how I feel.

“They may not be able to produce the same kind of works again and it was my hope that there would be more memorable works in the future, but that may be impossible now and that is very saddening.”

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Kyoto Animation, also known as KyoAni, was founded in 1981 as an animation and comic book production studio.

The company does work on films and TV productions, but is best known for its mega-hit stories featuring high school girls.

The tales are so popular that fans make pilgrimages to some of the places depicted.

Speaking after the fire on Thursday, company president Hideaki Hatta: “My heart is in extreme pain. Why on earth did such violence have to be used?”