What would inspire these "teens" to commit a copycat crime by targeting vehicles on the highway with slingshots instead of guns?

http://www.mysanantonio.com/news/crime/article/Police-Man-detained-in-freeway-shootings-isn-t-6501583.php

In September 2015 someone with a gun shot at and hit 11 vehicles on a busy highway in Phoenix Arizona. In 2005 and 2006 similar incidents happened in Phoenix.

Now three teenagers have been arrested for "COPYCAT" incidents....however they used Sling shots instead of Guns.

"Random bullets fired by snipers are among the most terrifying in American history. The 2002 Beltway sniper attacks killed 10 and gripped the Washington, D.C. metro region in fear. In 2012, a mentally disturbed man terrorized motorists along the I-96 corridor in Michigan, shooting at at least 23 cars he believed were part of a government conspiracy."

When is this going to stop? Why is this happening? What can be done to thwart this sort of thing to continue to happen?

Here is the original story of the shootings in Arizona that started last week that led up to these stupid kids copycatting this gunman.

http://www.usatoday.com/story/news/2015/09/11/phoenix-highway-shootings-echo-previous-roadway-attacks/72095612/