You were trying to ace the Hunter exam, but he threatened your life in the sky tower(or smth like that idk)... You were trying to escape from him but you were in more danger now...

Killua: "If you move, you die. If you talk, you die. If you try to escape, you die."

You thought it was the end of your life.. but then Gon sees this

Gon: "Killua, what are you doing..?!"

Killua: "..."