Thanks for your question. Self-regulation is a critical skill for long term social and emotional success. Even though your son has an awereness of his emotions and been taught some strategies to assist him regulate his emotions, it seems he can't apply them in moments of a full blown stress response as he has been 'emtionally hijacked". In these moments it literally makes it impossible for his brain to act in a rational and logical manner.
I would want to understand more about "what is the message behind the behaviour?" by talking with him. In addition, it might be of value to work with a psychologist to learn more re-emptive strategies to ward off a full blown resposne. Then in everyday moments you can emotion coach him until he learns to apply the skills for himself.