In the hour before he stepped out onto the second-floor balcony of the Lorraine Motel in Memphis and became the most famous martyr of the civil rights movement, Martin Luther King Jr. started a pillow fight.

Andrew Young, the former ambassador to the United Nations, Georgia congressman and mayor of Atlanta, told ABC News that King instigated the mischief in a ground-floor room where his brother, A.D. King, was staying on April 4, 1968.

"When I walked in the door, he [Martin Luther King Jr.] said, 'Where have you been? You haven't called me all day long,'" said Young, who had been working with King on civil rights issues since 1957. "I said, 'Well, I've been in court.'"

Earlier that day, Young had testified in federal court to get a restraining order lifted on the march in support of Memphis sanitation workers, who had been on strike since early February.

"He said, 'Well, you need to find a way to get me a message,'" said Young, adding that A.D. King and Ralph Abernathy, co-founder of the Southern Christian Leadership Conference and a longtime cohort of Martin Luther King Jr., were also in the room. "I said, 'I was on the witness stand trying to get you the right to march and keep you out of jail.'"

Martin Luther King Jr. responded, "'Oh, you're getting smart with me' and he picked up a pillow and threw it at me," Young said. "And he was in a more playful mood than I had seen him in years, I mean, acting like a child. I threw the pillow back and then everybody else picked up pillows and started beating me up. It was like a bunch of 12-year-olds."

About that time, the Rev. Samuel Billy Kyles, a Memphis minister, knocked on the door, to tell Martin Luther King Jr. and the others they were late for dinner at his house, Young, now 86, recalled.

Young remembered Martin Luther King Jr. saying, "'Well, let me go upstairs and put on my shirt and tie.'"

"I don't know that it makes any difference now, but that room downstairs in the corner had originally been his room," Young said. "And the Memphis Police asked the hotel manager could they move him upstairs because they thought they could protect him better upstairs than on the ground floor. Nobody was complaining or anything, but he couldn't have been shot in that downstairs room."

Police had every reason to be worried about protecting Martin Luther King Jr. About a week earlier, he had led a large demonstration in Memphis for the sanitation workers, who began their strike for better wages and work conditions after two workers were crushed to death by a malfunctioning garbage truck. The demonstration on March 28, 1968, had ended in violence. Stores were looted and a 16-year-old boy was shot and killed by police.

Memphis Mayor Henry Loeb III had imposed martial law and called in the National Guard to keep the peace.

Mountain top speech

Young said that when Martin Luther King Jr. arrived back in Memphis on April 3, he was battling a bad cold and fever and didn't feel up to giving a scheduled speech that night at the Mason Temple Church in Memphis. He asked Abernathy to speak for him, Young said.

"When we got there, the church, which seats 11,000 people, was full and people were standing all over and around outside in the rain. So we had to send somebody back to pick him [Martin Luther King Jr.] up," Young said.

"So Ralph starts speaking and when he came in, of course, everybody disrupted Ralph's speech," he said. "So he got up and started this speech that ended [with] that he'd been to the mountaintop."

In the speech, the 39-year-old Martin Luther King Jr. spoke of his own mortality, telling the crowd, "Like anybody, I would like to live a long life; longevity has its place. But I'm not concerned about that now. I just want to do God's will. And He's allowed me to go up to the mountain. And I've seen the Promised Land. I may not get there with you. But I want you to know tonight, that we, as a people, will get to the Promised Land. So I'm happy, tonight."

The speech, which would be Martin Luther King Jr.'s last, proved eerily prophetic.

Single shot rang out

When Martin Luther King Jr. finished pummeling Young with pillows that fateful Thursday afternoon at the Lorraine Motel, Young waited downstairs for his friend to come out of Room 306 and join him on the ride to dinner at Kyles' house.

"When he came out of the room, I was down in the parking lot and I said, 'You know, it's still kind of cool and you had a cold, you weren't feeling good last night. Why don't you bring your top coat?'" Young said.

"And he sort of lifted his head to say, 'I don't really ... do I need a coat?' And the shot rang out," Young said.

The time was 6:05 p.m.

Remembering that Martin Luther King Jr. had been in a playful mood earlier, Young said he thought he was "clowning" or that someone had lit a firecracker.

"And I looked up and saw that his shoes were still caught in the banister and he'd been sort of knocked out of his shoes," Young said. "And when I ran up there, I saw that he was ... there was a very clean wound that severed his spinal cord and the blood was all around him. I don't even think he heard the shot or felt any pain."

Young said Martin Luther King Jr. still had a pulse, but he knew his friend was gone.

"Basically my reaction was that, 'OK, so you've gone to Heaven and you've left us here in hell,'" Young told ABC News.

He said that in the immediate aftermath of the shooting, police officers swarmed the motel.

In a famous photo taken by Time magazine photographer Joseph Louw, Young is seen standing near Martin Luther King Jr.'s body on the balcony with Abernathy, Kyles, the Rev. Jesse Jackson and an 18-year-old Memphis State University student in bobby socks named Mary Louise Hunt. They are all pointing in the direction the shot came from, Young said.

"The police were all over on the other street and they were running toward us with their guns drawn and we were saying, 'The shot came from over there,'" Young recalled. "Instead of going to where the shot came from, they were coming to see about us."

Martin Luther King Jr. was rushed to St. Joseph's Hospital, where he was pronounced dead about an hour after he was felled by an assassin's bullet.

Call to widow

It was left to Young to call Martin Luther King Jr.'s widow, Coretta Scott King, who was at home in Atlanta, to break the news. He said he couldn't go through with telling her that her husband was dead.

"I said he was shot, but I didn't tell her how bad it was," Young said.

As police and the FBI launched a manhunt for Martin Luther King Jr.'s killer, which would eventually lead to the capture of James Earl Ray two months later in London, Young and other members of Martin Luther King Jr.'s inner circle reconvened the day of the killing back in Martin Luther King Jr.'s room at the Lorraine Motel.

That evening, Young and the others decided to carry on Martin Luther King Jr.'s fight for racial and economic equality.

Commitment to fight on

"It's something we had to do. We had no choice," Young said. "I think we were all committed. One of the movement's philosophies was that if somebody was struck down doing good, whatever you were doing you had to stop it and continue his works. So as soon as we came back from the hospital, we met back in his room and decided that we would have to carry on.

"And for 50 years, we've done that," he said. "Even though his body is no longer with us, his spirit is. I've been all over the world, and I've never been any place where somebody didn't ask me about Martin Luther King, and that's more than 150 countries. He has had a continued impact on the world."