Japan’s Prime Minister Shinzo Abe tweeted condolences, describing the attack as “too appalling for words.” It is the country’s worst mass killing in decades.

Kyoto Animation’s chief executive Hideaki Hatta, who started the company in 1981 with his wife Yoko, said in a statement, “I am heartbroken. It is unbearable that the people who helped carry Japan’s animation industry were hurt and lost their lives in this way.” Hatta also told reporters that the studio had recently received anonymous emails that told the studio “to die.”

Police apprehended a 41-year-old man who allegedly poured a flammable liquid inside the building before igniting it. His identity or reason for attacking the studio have not been revealed at this time. Eyewitness reports from survivors claim that the man yelled “Die!” as he dumped the flammable liquid. Hatta confirmed that the attacker was not a current or former employee of the studio.

Music producer Suguru Yamaguchi posted on Twitter that one of the studio’s star directors, Naoko Yamada, has been accounted for and is safe. While there are unconfirmed rumors floating around online about others who died in the event, the names of the deceased have not been released at this time.

Kyoto Animation is a producer of animated features and tv series with a focus on teen and youth stories. Their projects include the feature A Silent Voice and the series Sound! Euphonium.

Despite being a mid-sized studio, the company has significant influence in the industry, thanks to the popularity of its work. An in-depth history of the studio and its importance in the anime industry can be read on SakugaBlog. Kyoto has also been recognized for the positive treatment of its workers and for creating a healthy work environment; it pays its animators a regular weekly salary, rather than the Japanese industry norm of a per-frame rate, which puts undue pressure on artists. “It has a huge presence in animation here,” film commentator Yuichi Maeda told Reuters. “To have this many people die at once will be a huge blow to the Japanese animation industry.”

Fans of Kyoto Animation are sharing what the company’s work means to them on the Twitter hashtag #PrayForKyoani, while a fundraising campaign to help the studio rebuild has already raised over $800,000.

News of the attack has dominated the national news in Japan, as well as Japanese-language social media. When news of the fire first broke out, and before the fatalities had been announced, Your Name director Makoto Shinkai wrote on Twitter, “Everyone at Kyoto Animation, stay safe.”

Another Twitter user commented, “Would it get across to people who are not familiar with anime that the fire at Kyoto Animation studio is ‘a loss of culture,’ as if museums get destroyed by fire in an instant?”

Apple CEO Tim Cook also weighed in on Twitter, writing that the attack was “a tragedy felt far beyond Japan”: