I'm not over analyzing. It's pretty easy to put 2 and 2 together and figure out what they were going for. They didn't just happen to have three white kids holding rifles by chance.
Since no one pointed out the elephant in the room, I'll do it. Most gun crime is caused by non-Asian minorities. Only about 1 out of 8 people in the US are black, yet they cause over half the homicides. Source: http://bjs.gov/content/pub/pdf/htus8008.pdf
Notice how there's only three categories, white, black and other, and Hispanics are counted as white even though they're not. If you only count white gun crime it probably wouldn't be much different from Switzerland, a place with tons of guns and low gun crime. Chicago has some of the strictest gun laws, yet highest crime rates in the country, mostly caused by ethnic minorities. There are enough killings there per year to rival what Adam Lanza did almost 20 times over and that's just in one city. Seems to me America doesn't have a "gun" problem after all.
Sorry if what I'm saying here sounds harsh but you can't fix a problem until you deal with the cause and guns are not the cause of the problem here.