CHICAGO (CBS) — Fifty years ago tomorrow, civil rights leader Dr. Martin Luther King Jr. was assassinated in Memphis; thousands of people are traveling to Tennessee to mark the sad anniversary, including a prominent Chicago priest.

Rev. Michael Pfleger has a task he calls “intimidating.” He was invited to be the final speaker at a ceremony honoring Rev. King at the National Civil Rights Museum in Memphis, at the former Lorraine Motel where King was slain outside his hotel room on April 4, 1968.

“I speak up until 6:01, the moment he was killed, and then they’re going to have the bell ringing,” Pfleger said.

At first, Pfleger wanted to decline the invitation to speak.

“It is intimidating, and it’s frightening,” he said. “I’ve been to that room twice, and both times just wept.”

To fully understand why, you have to go back to 1966, when King spent most of the year living in Chicago, protesting racial segregation and discrimination in housing, education, and employment practices.

During an open housing march in the Marquette Park neighborhood, a teenage Pfleger saw his neighbors respond viciously to King’s protest.

“The hate, the racism, the taunting; they’re trying to turn over cars and start them on fire. I mean, throwing the rocks, throwing bottles,” he said.

Despite the violent response, King remained calm.

“I remember saying ‘This man is either really crazy, or he’s got some kind of power,’” Pfleger said.

King became Pfleger’s hero.

On April 4, 1968, while in college, Pfleger saw U.S. Sen. Robert F. Kennedy deliver the awful news of King’s assassination on television.

“I remember going into the church on the West Side of Chicago that I was working at the time, Precious Blood, and going in the sanctuary, and just crying like a baby; because this was my hero. This was my mentor. This was my vision of what I wanted to do with my life, and now what?” Pfleger said.

He determined the answer was to become a pastor himself. That path led him to St. Sabina Church, where Pfleger has been an activist who frequently speaks out about violent crime, discrimination, and education.

“People say to me today ‘Why are you a priest today?’ I say, ‘Because of Martin Luther King Jr.,’” Pfleger said.

On the spot where King was slain, Pfleger is set to give perhaps the speech of his life on Wednesday.

“It’s so overwhelming to think at that moment on that balcony, speaking. I hope I can hold it together,” he said.

Pfleger is close to the King family. He said King’s widow, Coretta Scott King, called Pfleger “her son.”

Many other Chicago area residents will head to Memphis to mark the somber anniversary of King’s assassination.

About 50 people boarded buses in Matteson on Tuesday to head south.

Trip organizer Maureen Forte said everyone from millennials to senior citizens were going to be part of the historic day.

“We have black, white, Hispanic. We’ve all unified together to make this delegation very powerful. We’re speaking. This is a movement, it’s not a moment. Today is a movement. So it’s a powerful day,” she said.

Organizers in Tennessee have said they expect more than 15,000 people to attend events marking the anniversary of King’s death.