World mourns Muhammad Ali, "The Greatest of All Time"

Tributes poured in early Saturday for Muhammad Ali, the legendary boxer and humanitarian who died at age 74 after a decades-long fight against Parkinson's disease.

It didn't matter if you were a boxing fan ...

"He was a champion, world champion boxer but he was also a world champion for the people because he was loved by the people," said a boxer at Gleason's Gym.

...or a music legend like Paul Simon, who announced Ali's death during a performance in Berkeley, Calif.

"I think you can very easily make the argument that we lost the world's greatest human being yesterday when he passed away," celebrity chef Andrew Zimmern told CBS News.

The reaction was immediate and the sentiment was consistent -- everyone felt the loss.

Even before the news was confirmed by his family, word of Ali's death began spreading like wildfire. In a controversial moment at a Miami Marlins baseball game, Ali's death was announced more than two hours before it was official.

"It's not a wonderful feeling to wake up and your friend is gone," George Foreman told CBS News. "I miss him. He was beautiful. Probably one of the best friends I've ever had, and even a brother to me for so many years," he said.

Foreman and Ali were once arch enemies, after Ali knocked Foreman out in the famous "Rumble in the Jungle" boxing match.

"I travel all over the world ... and I'd often hear that word no matter where I went: 'Ali. Ali. Ali!' Oh, I got tired of that! But in reality, he was a gift to the world. He wasn't anything but the greatest, the best in the world. And most of them never saw him box. They just for some reason had this thrill and love for Muhammad Ali."

But years later the two titans became the best of friends.

"I had a lot of conversations with Muhammad throughout the years, and of course he had to contend with Parkinson's. But I never, in all the conversations did he tell me, 'George, I'm suffering.' He delighted in every day he lived. He knew at some point that hey, I'm not the old Muhammad Ali, but I can still do magic! And I can't speak well, but I can still smile," said Foreman.

Gene Kilroy was Ali's manager, close friend and member of his inner circle.

"He said, 'I'm gonna live until God takes me. When he's ready, I'm ready. I'm not gonna argue with God,'" Kilroy said, adding, "the real Muhammed Ali was a shy, sensitive, humble guy."

Kilroy was there for the ups and downs, and says the champ's greatest triumphs were the moments when he was able to help others.

"He believed in freedom, justice, equality. He believed in a peace ... in no war," he said. "...he was always a man of great principal, he took no shortcuts... He took a stand. No one ever took a stand. He took a stand and lived and died by it."

"When he died yesterday, it was earth's gift to heaven," said Kilroy.

A sentiment shared by the President and first lady summed it up for many. They said they were grateful to God "for how fortunate we are to have known him, if just for a while; for how fortunate we all are that The Greatest chose to grace our time."

Then, it seems, the whole world took to Twitter -- where former opponents, fellow athletes, celebrities and strangers honored Ali for his strength and perseverance -- both in and out of the ring.

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• Obituary