FIFTEEN years ago today, the bombing of the Alfred P. Murrah Building in Oklahoma City claimed the lives of 168 men, women and children. It was, until 9/11, the worst terrorist attack in United States history. But what emerged in its aftermath  the compassion, caring and love that countless Americans from all walks of life extended to the victims and their families  was a powerful testament to the best of America. And its lessons are as important now as they were then.

Most of the people killed that day were employees of the federal government. They were men and women who had devoted their careers to helping the elderly and disabled, supporting our veterans and enforcing our laws. They were good neighbors and good friends. One of them, a Secret Service agent named Al Whicher, a husband and father of three, had been on my presidential security detail. Nineteen children also lost their lives.

Those who survived endured terrible pain and loss. Thankfully, many of them took the advice of a woman who knew how they felt. A mother of three children whose husband had been killed on Pan Am Flight 103 in 1988 told them, “The loss you feel must not paralyze your own lives. Instead, you must try to pay tribute to your loved ones by continuing to do all the things they left undone, thus ensuring they did not die in vain.”

We are all grateful that so many of the attack’s survivors have done exactly that. We must also never forget the courageous and loving response of the people and leaders of Oklahoma City and the state of Oklahoma, as well as the firefighters and others who came from all across America to help them.