How you can help prevent mass shootings

In the weeks and months after September 11, 2001, Americans were laser-focused on their surroundings, galvanised and determined to prevent another attack

In the summer of 2013, I led a briefing with Attorney General Eric Holder on the F.B.I.’s research on active-shooter incidents in the United States. Our meeting took place just months after a gunman massacred six adults and 20 children at the Sandy Hook Elementary School in Newtown, Conn.

“If these were deaths from terrorist acts, the American public would be outraged,” Mr. Holder said. I couldn’t disagree.

Four years later, his observation still haunts me. Last month, 59 people were mowed down in Las Vegas at a country music concert. This week, we are facing the gut-wrenching news that an 18-month-old