NASHVILLE — Dear Mr. Lewis, I write with a heavy heart. Stage 4 pancreatic cancer is a brutal diagnosis, so it’s no surprise that last Sunday night the internet erupted with anguish as news of your illness became public. Treatment may give you a “fighting chance” to continue working “for the Beloved Community,” as you wrote in a statement, but it’s painful to think of what you will be called on to bear in the coming months. You have already borne so much for us.

In the National Civil Rights Museum in Memphis, a massive screen plays a montage of film and still photos from March 7, 1965, a day now commemorated as “Bloody Sunday.” The images were made at the beginning of a planned march from Selma to Montgomery, Alabama’s capital, to claim voting rights for the African-American citizens of the state. I grew up in Alabama, not far from Selma, and I’ve always known the story of Bloody Sunday, but knowing the story is not the same thing as watching it unfold on a life-size screen. Standing in the National Civil Rights Museum on Martin Luther King Jr. Day a few years ago, I watched in horror. What you and your fellow marchers, 600 strong, found waiting for you on the other side of the Edmund Pettus Bridge was 150 state police and local law-enforcement officers armed with billy clubs, bullwhips and tear gas. They gave you two minutes to disperse.

As the chairman of the Student Nonviolent Coordinating Committee, you were standing at the very front of the march. You were wearing a light-colored trench coat, and that coat is what makes it possible to follow you in the black-and-white footage of those next chaotic moments. One minute and five seconds after the two-minute warning, evil advanced and the carnage began, even as you knelt in the road to pray.

The beating you took that day from an Alabama state trooper may have fractured your skull, but it didn’t crack your resolve. National news stories carrying photos and film footage from Bloody Sunday finally woke this nation to what was happening in the Jim Crow South, and that awakening ultimately led to the passage of the Voting Rights Act five months later.