You might be right ╮( ̄▽ ̄)╭ but I don't think he's just angry and that one phrase we can see in the prologue might not his thoughts at that exact moment but just an impact phrase. And even in the prologue his eyes seemed out of focus like when he hurt Lucaon and when that girl finds him he really doesn't seem to realize what is happening because he thinks "Blood everywhere..."
Well yeah his eyes are out of focus cuz he lost so much blood. And what impact statement? Those are his thoughts as we've always seen them: in thought boxes, through his perspective. Never a narrator. I read the raws so I know he's not being controlled. Also, Cecelia did an examination with her ability remember? He's not being controlled ( ̄∇ ̄")

Ok, so whoever is controling ma baby Kyon, is clearly aiming for Lucaon. Kyon is trying to save Lucaon now by leaving but he didn't seem conscious when he hurt himself. So my theory is that the Introm who is controling Kyon, after noticing that he is important to Lucaon, made Kyon kill himself to affect Lucaon and turn him into a zero. We can notice that he is already fighting against it after Kyon said he'd leave.