Why Do We React So Violently?

I was shocked and devastated this morning when I was scrolling through CNN and found and article titled "Florida boy kills one brother, wounds another after food fight" At first I was a little confused because when I saw food fight, I thought your normal high school cafeteria scene.  However, upon reading it, I thought the reason he killed his brother was just as silly.  

The three boys were home eating dinner with their mom and oldest brother gone.  They reportedly got in an arguement about food, the details of which were not given.  After their spat, the 13 year old boy got up and shot and killed his 6 year old brother, and shot and wounded his 16 year old brother.  He then took the handgun and turned it on himself, committing suicide.  The 16 year old brother was hurt, but able to call 911 and get help. 

 It is devastaing to think that this family will have to deal with the loss of their two youngest brothers.  However, I was completely shocked that all of this tradegy stemmed from what seems to be a simple argument.  It makes me wonder what messege society is conveying to young minds.  Why do we think that it is ok after an argument to go and shoot your brothers? I know it very well might have come from a deeper problem, but it is still very disheartening to me that a 13 year-olds first reaction is to grab a gun and kill everyone.  I hope that this isn't some idea that he got from media, because if so, I think something really must be changed.  Media influences so much of what people do, but if it is harming others I think it has gone too far.