WYOMING, Del. — By his own account, Toby Lopez was a supremely ordinary guy. He sold Toyotas and lived with his mother in a tidy rancher here with a cherry tree out front. He was proud that he could connect with customers — anyone from a Superior Court judge to, as he put it, “Redneck Bill from down on the farm.” What passed for excitement was the time his young niece won a beauty contest and he chauffeured her in a red Corvette in a local parade.
Then a high school friend was killed in Afghanistan, and the Islamic State began beheading American journalists. Horrified, Mr. Lopez heard on CNN one day in the fall of 2014 that the Islamic State was active on Twitter, and he went online to see what he could find. “I was intrigued,” said Mr. Lopez, 42. “What could they possibly be saying on Twitter?”