You were 12 years old at the time. Individuals at that age understandably do not have the level of awareness and understanding that they possess in adulthood. You, at 12 years old, had no way of knowing that your behavior and remarks would have elicited the reaction that happened. It was not your intention to cause someone to react the way that he/she did... Intention is very important to account for when evaluating and reflecting back on experiences and actions.

You are not experiencing the same state of consciousness (and level of awareness) as you were when you were 12 years year old. You are no longer that 12 year old. What transpired between you and your family member was simply an experience. A temporary/transient experience. It's nothing that you can hold onto, and it's not something which can constitute any sense of identity for you. When I say it was an 'experience' - it's quite functional and helpful to frame it as a learning experience. Contemplate and ask yourself what you could have learned (gained) from having gone through that experience? When you can work this out within your awareness - you can frame the experience in a functional/positive light, and doing this will eventually transmute your preexisting reaction/perspective...

Perhaps that experience influenced you to become more sensitive or considerate of other peoples' emotional states? You said that your relative hasn't been violent for quite some time (nearly a decade)? That would bring that person back to within a couple/few years of that particular incident. Perhaps that particular outburst and physical interaction with a family member (who was a child at the time) ended up really bothering/disturbing that individual - and that mental/emotional reaction played a role (served as a catalyst) for that person to later evaluate their own behavior (state of being) and make changes for the better (becoming less angry/violent)...

Also worth noting - that person is not experiencing the same state of consciousness (level of awareness) anymore either... Neither of you are the same as you were when that interaction transpired. You can't cling to those old identities - because they don't really exist...

Why is this coming up now? Because there is stil residual mental/emotional 'baggage' (energy) left over from that life experience. Something which wasn't fully processed and released. Something which is still being stored inside you. It's quite common and natural for children to suppress and even repress difficult and challenging emotions that are experienced during their youth only to have that same emotional energy resurface later in life - it absolutely happened in my own life. That film triggering this reaction in you will eventually end up being viewed by you as a 'blessing in disguise'... There is transformational healing to be done - and when that happens, you will find yourself experiencing an entirely new state of consciousness (state of being).

Find the silver lining in that life experience! How can it be viewed (perceived) as a learning experience and ultimately a facilitator of conscious growth (evolution)? That's what you have to connect with here. This will faciliate the healing process and eventually any residual mental/emotional energy connected to the experience will fully surface and be purged (released) once and for all.

You said you keep thinking about it every moment and it's driving you mad. WRITE OUT everything that's on your mind concerning these circumstances. It's very cathartic. No one has to read it but your eyes only. You don't even have to save what you write - it's the writing process that facilitates healthy processing of thoughts/emotions that are afflicting us. You have to get it 'out there' and off your chest. The distraction strategy won't work and will only be delaying the inevitable. Just write everything down with no filtering or censoring on your part. Read over what you write - it will help you reflect upon and be more aware of what's unfolding. You said you don't know what you're supposed to do to 'get rid of it'.... You are going to steer/guide yourself towards an internal 'place' (state) whereby you will finally allow yourself to consciously acknowledge and experience (process) whatever it is that you've been holding onto inside of you. A very significant emotional release (purging) will transpire, and once that happens, you are going to feel like a serious weight was lifted off your shoulders - and you will lighter. It's all going to be worth it... Keep going!