The story said, "?The 4-year-old was angry, he went and got the gun, put it to his brother's head and shot the gun,". The problem is that the child's reaction when angry was to kill the other child.
It strikes me that if there were not a gun present in his rage he probabally might have done something like grab a butcher knife from the kitchen and stab the other child. I doubt that a 2 year old would have lived thru that either. The problem in not a gun, knife, or any other physical object, it is that kid's kill reaction when angered.
Of course, had the kid grabbed a butcher knife as in the senario I mentioned, I doubt that JP Bill would have bothered to post the story.