As for my reasoning, I think the kid is unstable. I've been in fights and I've been in a similar situation where I was jumped by 3 black kids. I have good feet and my friends were nearby so the situation eventually turned around on the assailants. As for why this experience is relevant. I've never felt in any time during those attacks or fights that I was under danger of losing my life. Nor do I think that one punch pushes someone to the "brink". No. Instead this fellow is more likely unstable and this stabbing was due to him "snapping". If he snaps once he's probably going to snap again.