That's the stupidest fucking thing I've ever read, and knowing this author, he probably didn't intend for that to be the case. Nut case chunibyo thinks he'll be the first person to kill without a reason. 1st off, murder can't be done without intent, even if your reason is just "I felt like it." Technically that's still a reason, and if dipshit thinks that isn't a reason, then sorry kiddo but people have been doing that for a long time so you won't be the first lol.
Edit: We shouldn't be at all surprised though since this series has been edgelord trash since day one, and there was never gonna be anything interesting behind why this dude is cartoonishly evil.