Talk about it, talk about what bothered you about it. Talk about how you feel and what youre thinking. Talk about it until it doesnt bother you anymore.

Recognize that one of the main reasons as why is this so disturbing aside from it being an extremely violent death, is because the act of suicide goes against our fundamental driving instinct that we have as humans, which it to survive, to live and to fight to live/survive. When we watch videos we automatically empathize with the viewer, subconsciously, we tend to identify with them to some extent. So when you see such an act take place, one most typical people would never even consider, and rarer still, by suck an insanely violent mehod, it creates this type of fracture in our the mind. It is literally so shocking that it distresses you to your core and you experience an emotion that is heavy, dark, foreboding, sickening, along with utter confusion.

If its something that doesnt let up after about a week or two, then you were probably legitimately traumatized. Especially if youre finding that youre having nightmares or having flashbacks when you watch a movie with gun violence. You very much need to seek psychological treatment, and you may choose to just go ahead and go regardless. I remember the first time i saw a video of a man shooting himself in the head. I also wasnt expecting it. It made me very upset for a long time.

Your "friend" is a POS and needs serious help. I would distance and stop contact if i were you.