The world will always remember what happened at Columbine High School in Littleton, Colorado, twenty-one years ago, yesterday. The Columbine High School massacre, at the time, was the deadliest school shooting in the history of the United States. Unfortunately, since then, the tragedies at Virginia Tech University, Sandy Hook Elementary, and Umpqua Community College have replaced that title. Today, sadly, these schools are synonymous with the nationwide grief and loss of their respective mass-shootings.

By the time the guns were silenced, on April 20th, 1999, two high school students had entered Columbine High School and had murdered thirteen people – twelve students and one teacher – before taking their own lives. Twenty-one other people were injured. A day the world will never forget.

Principal, Frank DeAngelis, was in his office meeting with a teacher when a secretary rushed to tell him about reported gunfire at the school. Frank ran into the hallway and saw two gunmen at the other end of the long main corridor. What happened in the next few moments seemed to occur in slow motion, the scene forever etched in his memory.

Frank saw explosions of light, heard bullets ricochet off walls, and watched a glass trophy case shatter. He stared at shotgun pointed in his direction and was certain he was about to die. Then, he noticed a group of students in a side hallway and rushed to usher them out of the line of fire. The gunman, at that moment, inexplicably, turned and decided to run up a staircase.

What many don’t know is the business teacher and basketball coach who was killed, Dave Sanders, was Frank’s best friend. He was the teacher the gunman had chased up the stairwell, mysteriously, sparing Frank’s life.

By the time of the shootings, Frank DeAngelis had already spent two decades at Columbine, as a history teacher, baseball coach, assistant principal, and principal. He responded to the shootings by asking the student body to help him rebuild the school and restore a sense of community. He promised that he wouldn’t quit his post until everyone, who then, was in high school had graduated.

There’s a part of this story that, for most, has remained untold. What many don’t know is when those, then, freshmen graduated in 2002, Frank made another promise. Realizing that his work wasn’t done, he committed to stay on the job until all the children, who were in kindergarten, in 1999, had also graduated from high school. In 2012, with Frank at the helm, Columbine graduated the class of seniors, who had been kindergarteners at the time of the tragedy. I had the honor of speaking to the class of 2012; it was a moment that I will never forget.

In the fifteen years between the day of the Columbine tragedy and his retirement, Frank helped transform the site of one of America’s darkest moments into a beacon of light, hope, and promise. He did it by making a commitment to always act out of love and to teach his students and staff to do the same.

I’ve visited Columbine High School many times to see my dear friend Frank or to speak to his students. And I’ll tell you: I’ve never been inside a public high school, like Columbine, where you can smell, feel, and taste acceptance and grace in every corner of the building.

There are five men in my life that have unequivocally, shaped, who I am, as a person today. One of those men is Frank DeAngelis. Five years ago, Frank and I were attending our National Leadership Academy’s annual Book-n-Benefit business breakfast, where Frank serves, as our honorary Chairman. The keynote speaker, Marshall Goldsmith, challenged the audience of three-hundred business leaders to make a commitment to serve something, or someone, beyond themselves, and then, he asked all of us to remain dedicated to this promise each and every day for the rest of our lives. I immediately thought of doing the rosary every morning, paying a kind compliment to my wife, or telling my kids that I believe in them.

Do you know what Frank decided that morning? To send me a text message EVERY morning, with a bible verse, an inspirational quote, and a note to tell me that he loves me. And for the last 1,825 days – Frank has kept his promise. I’ve never started my morning, within the last half-decade, without a message from Frank DeAngelis telling me he loves me. It’s no joke; I think Frank has told me he loves me more times, than my own wife!

Commitment is a dying word. We live in a different world since the internet, social media, and smartphones have hijacked our lives. But, not Frank. He has taught me that the biggest gift we can give our family, friends, neighbors, employees, customers, and clients is our word. And our word is only a promise. However, our actions… they are our commitment.

So today, my friends, let’s make a promise to ourselves to make a commitment to serve others. Think about one thing you can do every day for the next month. Call a friend going through a divorce. Write a heartfelt letter to someone on your mind. Share a generous act of kindness with a complete stranger. Mail a copy of your favorite book to your favorite customers and clients.

Perhaps, this one month of kindness can turn into two months? And perhaps, these two months can turn into two years. One thing is for certain, when you invest in the lives of others, your life will change for the better. Your investment has the power to positively transform all of the personal and professional relationships in your life that are meaningful to you.

The world may remember Columbine High School by what happened on April 20, 1999. But, I choose to remember Columbine by what happened from that day forward. And the man that not only made his promise to the students and community at Columbine, but also, backed it up with his commitment to change thousands of lives – including mine.