(CNN) Former President Barack Obama joined civil rights icon Rep. John Lewis to reflect on the legacy of Martin Luther King Jr. 50 years after his assassination.

In a six-and-a-half minute video, shot in black and white, Lewis recalled learning that King had been shot while campaigning for Robert Kennedy in Indianapolis.

"The thing I regret more than anything else is I probably didn't spend enough time with him and learning from him. I thought he would be around a long time," he said.

Obama and Lewis visited with young men from Ron Brown College Preparatory High School in Washington, DC, for a My Brother's Keeper Alliance roundtable discussion. The video was earlier reported by Time magazine.

Lewis, who Obama called "one of my inspirations to get into public life," shared his memories of King and the civil rights movement, including speaking at the March on Washington.

Read More