An attacked entered the studio spread fuel all over the place.Yelled "DIE!" and set the studio on fire.

Apparently he claimed that they had plagiarised a novel he wrote. Whatever the reason he had for carrying out this attack, it's a terrible sad loss of life. Something you don't expect to happen in Japan.

I wouldn't even be surprised if the claim of plagiarism was true (I am not accusing the studio... I simply can't rule it out either), since big studios do not have the best of reputations when it comes to the copyrights of still unknown people, yet setting the entire place on fire, and the people killed most likely not even being aware of the entire situation, was not really the best way to resolve such a thing.
I really wonder what the claim was based upon, though....

But indeed 30+ people needlessly killed..... shocking.... absolutely shocking....