Writes Daniel Byman in The Wall Street Journal:
Americans are now learning what citizens of Indonesia, Saudi Arabia, Spain, the United Kingdom, and other foreign countries have long known: that some of our own can and will go to great lengths to kill their fellow citizens.
The U.S. is facing rising terror threats from its own citizens. What made the country safer after 9/11 is changing, and not for the better.
The police and army cannot be everywhere. The only way to fight terrorism at home is via alert, responsible, aware, and armed civilians.
