and they figure out exactly why that guy did it and what happened and why. A court trial should be able to decide that.

Any normal human being would react like that to a real event, and yes it is a scary thing to see someone die that way.

I've played D&D, Traveller, and other RPGs that simulate violence. Only I knew that they were just paper and pencil and dice, fake violence, acting, etc. At the end of the session nobody really died and nobody really got hurt (except for hurt feelings if someone loses in the game or their character dies). It might be good advice to avoid simulated violence, and not watch the news and other things with violence in them for a while.