The US is a violent country. It kills people by the thousands on a regular basis and its preferred manner of dealing with its opponents is to destroy their regimes. During the presidential elections Obama boasted that he personally supervised the drone attacks and gave the orders which killed thousands of non-combatants in Pakistan, Afghanistan, and Yaman. That's where the change should start. How can you blame ordinary killers when their chief glamorizes it?
First refugees travelling on Hungarian bus arrive at Austrian border (Reuters)
from the article: Stop the slaughter, change U.S. gun laws now