He was fast of fist and foot -- lip, too -- a heavyweight champion who promised to shock the world and did. He floated. He stung. Mostly, he thrilled, even after the punches had taken their toll and his voice barely rose above a whisper.

He was "The Greatest."

Muhammad Ali died Friday, according to a statement from his family. He was 74.

"We lost a legend, a hero and a great man," Floyd Mayweather told ESPN.

Ali had been hospitalized in the Phoenix area this week with respiratory issues, and his children had flown in from around the country.

One of them, Rasheda Ali, took to Twitter early Saturday morning to mourn her father.

The Greatest Man that ever lived. Daddy my best friend & my Hero You R no longer suffering & now in a better place. pic.twitter.com/IASO4u3Ikn — RASHEDA ALI™ (@rashedaali) June 4, 2016

Another daughter, Hana Ali, described her father's last moments on Instagram on Saturday, saying his heart wouldn't stop beating for 30 minutes after all of his other organs failed.

"No one had even seen anything like it," she wrote, calling it "a true testament to the strength of his spirit and will."

She said the family was surrounding Ali, hugging and kissing him, holding his hands and chanting an Islamic prayer.

The Paradise Valley Police Department told ABC News that an emergency medical services call was made from Ali's address in the Phoenix area on Tuesday, and the Phoenix Fire Department confirmed that it responded at that time to a call for mutual aid for a 74-year-old male with respiratory issues.

Retired from boxing since 1981, Ali had battled Parkinson's disease for decades. He had been hospitalized a few other times in recent years, including in early 2015 because of a severe urinary tract infection initially diagnosed as pneumonia.

Ali had looked increasingly frail in public appearances, the last coming April 9, when he wore sunglasses and was hunched over at the annual Celebrity Fight Night dinner in Phoenix, which raises funds for treatment of Parkinson's.

He had been living quietly in the Phoenix area with his fourth wife, Lonnie, whom he married in 1986.

Ali's funeral will be held in his hometown of Louisville, with further details to come, spokesman Bob Gunnell said. The city put flags at half-staff Saturday morning.

Ali's death reaches far beyond the sport of boxing. He was one of the world's most recognized people for his actions in and out of the ring. His stance on the military draft and his conversion to Islam polarized America, mainly along racial lines. Yet later, he unified people with his messages of freedom, peace and equality.

"Muhammad Ali was The Greatest. Period," President Barack Obama said in a statement released Saturday morning. "If you just asked him, he'd tell you. He'd tell you he was the double greatest; that he'd 'handcuffed lightning, thrown thunder into jail.'

"Like everyone else on the planet, Michelle and I mourn his passing. But we're also 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.

"... Muhammad Ali shook up the world. And the world is better for it. We are all better for it."

"Muhammad Ali shook up the world. And the world is better for it. We are all better for it. Michelle and I send our deepest condolences to his family, and we pray that the greatest fighter of them all finally rests in peace." President Barack Obama

Reaction to the news was immediate.

"A true great has left us," said Bob Arum, who promoted 27 Ali fights. "Muhammad Ali transformed this country and impacted the world with his spirit. His legacy will be part of our history for all time."

Said Cavaliers star LeBron James: "The reason why he's the GOAT [greatest of all time] is not because of what he did in the ring, which was unbelievable. It's what he did outside of the ring, what he believed in, what he stood for -- along with Jim Brown and Oscar Robertson, Lew Alcindor, obviously, who became Kareem [Abdul-Jabbar], Bill Russell, Jackie Robinson. Those guys stood for something. He's part of the reason why African-Americans today can do what we do in the sports world. We're free. They allow us to have access to anything we want. It's because of what they stood for, and Muhammad Ali was definitely the pioneer for that."

Added Mike Tyson on Twitter:

With a wit as sharp as the punches he used to "whup'' opponents, Ali dominated boxing for two decades before time and Parkinson's disease, triggered by thousands of blows to the head, ravaged his magnificent body, muted his majestic voice and ended his storied career in 1981. He fought in three decades, finished with a record of 56-5 with 37 knockouts and was the first man to win heavyweight titles three times.

"It's a sad day for life, man," promoter Don King said. "I loved Muhammad Ali. He was my friend. Ali will never die. Like Martin Luther King, his spirit will live on. He stood for the world.''

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Despite his debilitating illness, Ali traveled the world to rapturous receptions even after his once-bellowing voice was quieted and he was left to communicate with a wink or a weak smile. Revered by millions worldwide and reviled by millions more, Ali cut quite a figure, at 6-foot-3, 210 pounds in his prime.

"Float like a butterfly, sting like a bee,'' his cornermen exhorted, and he did just that in a way no heavyweight had ever fought before. He whipped the fearsome Sonny Liston twice, toppled the mighty George Foreman with the rope-a-dope in Zaire and nearly fought to the death with Joe Frazier in the Philippines. Through it all, he was trailed by a colorful entourage who merely added to his growing legend.

"Rumble, young man, rumble,'' cornerman Bundini Brown would yell to him. Rumble Ali did. He fought anyone who meant anything and made millions of dollars with his lightning-quick jab. His fights were so memorable that they had names -- "Rumble in the Jungle'' and "Thrilla in Manila.'' But it was as much his antics -- and his mouth -- outside the ring that transformed the man born Cassius Clay into the household name Muhammad Ali.

"I am the greatest,'' Ali thundered again and again. Few would disagree.

"Muhammad Ali is a legend and one of the world's most celebrated athletes, the fighter who ushered in the golden era of boxing and put the sport on the map," Oscar De La Hoya said in a statement. "He paved the way for professional fighters, including myself, elevating boxing to become a sport watched in millions of households around the world.

"Beyond his incredible talent, he also made boxing interesting. Ali was fearless in the ring and took on the toughest, most challenging opponents. Ali exemplified courage. He never took the easy route, something to be admired in and outside of the ring."

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President Bill Clinton who awarded Ali the Presidential Citizens Medal, mourned Ali's death.

"Hillary and I are saddened by the passing of Muhammad Ali," Clinton said in a statement. "From the day he claimed the Olympic gold medal in 1960, boxing fans across the world knew they were seeing a blend of beauty and grace, speed and strength that may never be matched again."

Athletes, celebrities and dignitaries shared those sentiments. Manny Pacquiao called Ali "a giant." Tiger Woods, "a champion."

"Boxing benefited from Muhammad Ali's talents but not nearly as much as mankind benefited from his humanity," Pacquiao said.

You'll always be The Greatest for more than just what you did in the ring. A champion to so many people in so many ways. — Tiger Woods (@TigerWoods) June 4, 2016

Ali spurned white America when he joined the Black Muslims and changed his name. He defied the draft at the height of the Vietnam war -- "I ain't got no quarrel with them Viet Cong'' -- and lost three and a half years of the prime of his career. He entertained world leaders, once telling Philippines President Ferdinand Marcos: "I saw your wife. You're not as dumb as you look.''

He later embarked on a second career as a missionary for Islam.

"Boxing was my field mission, the first part of my life,'' he said in 1990, adding with typical braggadocio, "I will be the greatest evangelist ever.''

Ali couldn't fulfill that goal because Parkinson's robbed him of his speech. It took such a toll on his body that the sight of him in his later years -- trembling, his face frozen, the man who invented the Ali Shuffle barely able to walk -- shocked and saddened those who remembered him in his prime. But for his part, Ali didn't complain about the price he had paid in the ring.

Muhammad Ali defeated Sonny Liston to retain the heavyweight title in May 1965. It was one of his 56 career wins as a professional. AP Photo/John Rooney

"What I suffered physically was worth what I've accomplished in life,'' he said in 1984. "A man who is not courageous enough to take risks will never accomplish anything in life.''

The quiet of Ali's later life was a contrast to the roar of a career that had breathtaking highs as well as terrible lows. He exploded on the public scene with a series of nationally televised fights that gave the public an exciting new champion, and he entertained millions as he sparred verbally with the likes of bombastic sportscaster Howard Cosell.

Ali once calculated that he had taken 29,000 punches to the head and made $57 million in his pro career, but the effect of the punches lingered long after most of the money was gone. That didn't stop him from traveling tirelessly to promote Islam, meet world leaders and champion legislation dubbed the Muhammad Ali Boxing Reform Act.

Although slowed in recent years, he managed to make numerous appearances, including a trip to the 2012 London Olympics. Despised by some for his outspoken beliefs and refusal to serve in the U.S. Army in the 1960s, an aging Ali became a poignant figure whose mere presence at a sporting event would draw longstanding ovations. With his hands trembling so uncontrollably that the world held its breath, he lit the Olympic torch for the 1996 Atlanta Games in a performance as riveting as some of his fights.

A few years after that, he sat mute in a committee room in Washington, with his presence enough to convince lawmakers to pass the boxing reform bill that bore his name. Members of his inner circle weren't surprised. They had long known Ali as a humanitarian who wouldn't think twice about getting in his car and driving hours to visit a terminally ill child. They saw him as a man who seemed to like everyone he met -- even his archrival, Frazier.

One of his biggest opponents later become a big fan too. On the eve of the 35th anniversary of their "Rumble in the Jungle,'' Foreman paid tribute to the man who so famously stopped him in the eighth round of their 1974 heavyweight title fight, the first ever held in Africa.

Foreman weighed in on the loss of Ali early Saturday morning.

Ali, Frazier & Foreman we were 1 guy a part of me slipped away "the greatest piece" Muhammad Ali. — George Foreman (@GeorgeForeman) June 4, 2016

Born Cassius Marcellus Clay on Jan. 17, 1942, in Louisville, Ali began boxing at age 12 after his new bicycle was stolen and he vowed to policeman Joe Martin that he would "whup'' the person who took it. He was only 89 pounds at the time, but Martin began training him at his boxing gym. That was the beginning of a six-year amateur career that ended with the light heavyweight Olympic gold medal in 1960.

Ali had already encountered racism. On boxing trips, he and his amateur teammates had to stay in the car while Martin bought them hamburgers. When he returned to Louisville with his gold medal, the Chamber of Commerce presented Ali a citation but said it didn't have time to co-sponsor a dinner. In his autobiography, "The Greatest,'' Ali wrote that he tossed the medal into the Ohio River after a fight with a white motorcycle gang, which started when he and a friend were refused service at a Louisville restaurant.

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The story might be apocryphal, and Ali later told friends he simply misplaced the medal. Regardless, he made his point. After he beat Liston to win the heavyweight title in 1964, Ali shocked the boxing world by announcing that he was a member of the Black Muslims -- the Nation of Islam -- and was rejecting his "slave name.'' As a Baptist youth, he spent much of his time outside the ring reading the Bible. From then on, however, he would be known as Muhammad Ali, and his book of choice would be the Quran.

Ali's affiliation with the Nation of Islam outraged and disturbed many white Americans, but it was his refusal to be inducted into the army that angered them most. That happened on April 28, 1967, a month after Ali knocked out Zora Folley in the seventh round at Madison Square Garden in New York for his eighth title defense. He was convicted of draft evasion, stripped of his title and banned from boxing.

Ali appealed the conviction on the grounds that he was a Muslim minister. He married 17-year-old Belinda Boyd, the second of his four wives, a month after his conviction, and had four children with her. He had two more with his third wife, Veronica Porsche, and he and his fourth wife, Lonnie Williams, adopted a son.

During his banishment, Ali spoke at colleges and briefly appeared in a Broadway musical called "Big Time Buck White.'' Still facing a prison term, he was allowed to resume boxing three years later, and he came back to stop Jerry Quarry in three rounds on Oct. 26, 1970, in Atlanta, despite efforts by Georgia Gov. Lester Maddox to block the bout.

Ali was still facing a possible prison sentence when he fought Frazier for the first time on March 8, 1971, in what was labeled "The Fight of the Century.'' A few months later, the U.S. Supreme Court overturned his conviction on an 8-0 vote.

"I've done my celebrating already,'' Ali said after being informed of the decision. "I said a prayer to Allah.''

Many in boxing believe Ali was never the same fighter after his lengthy layoff, even though he won the heavyweight championship two more times and fought for another decade.

Perhaps his most memorable fight was the "Rumble in the Jungle,'' in which he upset a brooding Foreman to become heavyweight champion once again at age 32. Many worried that Ali could be seriously hurt by the powerful Foreman, who had knocked Frazier down six times in a second round TKO. But although his peak fighting days might have been over, Ali was still in fine form verbally. He promoted the fight relentlessly, as only he could.

Ali lit the Olympic cauldron at the Atlanta Games in 1996, one of his many post-fight career honors. Doug Mills/AP Photo

"You think the world was shocked when Nixon resigned,'' he said. "Wait till I whup George Foreman's behind.''

Ali won over a country before he won the fight. He mingled with people as he trained and displayed the kind of playful charm the world had already seen. On the plane into the former Congo, he asked what the citizens of Zaire disliked most. He was told it was Belgians because they had once colonized the country.

"George Foreman is a Belgian,'' Ali cried out to the huge crowd that greeted him at the airport.

By the time the fight went off in the early morning hours of Oct. 30, 1974, Zaire was his.

"Ali, booma-ya [Ali, kill him],'' many of the 60,000 fans screamed as the fight began in Kinshasa.

Ali pulled off a huge upset to win the heavyweight title for a second time by allowing Foreman to punch himself out. He used what he would later call the "rope-a-dope'' strategy -- something even trainer Angelo Dundee knew nothing about. Finally, Ali knocked out an exhausted Foreman in the eighth round, which touched off wild celebrations among his African fans.

"I told you I was the greatest,'' Ali said.

That sentiment was shared by NFL legend Jim Brown on Saturday:

"The world has lost a great Champion. Muhammad Ali, lover of human beings, a warrior for the fight against discrimination...a great friend." — Jim Brown (@JimBrownNFL32) June 4, 2016

That might have been argued by followers of Joe Louis or Rocky Marciano or Sugar Ray Robinson, but there was no doubt that Ali was just what boxing needed in the early 1960s. He spouted poetry and brash predictions. After the sullen and frightening Liston, he was a fresh and entertaining face in a sport that struggled for respectability. At the weigh-in before his Feb. 25, 1964, fight with Liston, Ali carried on so much that some observers thought he was scared stiff and suggested the fight in Miami Beach be called off.

"The crowd did not dream when they lay down their money that they would see a total eclipse of the Sonny,'' Ali said.

Ali went on to punch Liston's face lumpy and became champion for the first time when Liston quit on his stool after the sixth round.

"Float like a butterfly, sting like a bee,'' became Ali's rallying cry. His talent for talking earned him the nickname "The Louisville Lip,'' but he had a new name of his own in mind: Muhammad Ali.

"I don't have to be what you want me to be,'' he told reporters the morning after beating Liston. "I'm free to be who I want.''

Frazier refused to call Ali by his new name and insisted he was still Cassius Clay. So did Ernie Terrell in their Feb. 6, 1967, fight, a mistake he would come to regret through 15 long rounds.

"What's my name?'' Ali demanded as he repeatedly punched Terrell in the face. "What's my name?''

By the time Ali was able to return to the ring following his forced layoff, he was bigger than ever. Soon, he was in the ring for his first of three epic fights against Frazier, with each fighter guaranteed $2.5 million. Before the fight, Ali called Frazier an "Uncle Tom'' and said he was "too ugly to be the champ.'' His gamesmanship could have a cruel edge, especially when directed toward Frazier.

In the first fight, though, Frazier had the upper hand. He relentlessly wore Ali down, floored him with a crushing left hook in the 15th round and won a decision. It was the first defeat for Ali, but the boxing world had not seen the last of him and Frazier in the ring. Ali won a second fight. Then came the "Thrilla in Manila'' on Oct. 1, 1975, in the Philippines, a brutal bout that Ali said afterward was "the closest thing to dying'' that he had experienced. Ali won that third fight but took a terrific beating from the relentless Frazier before trainer Eddie Futch kept Frazier from answering the bell for the 15th round.

"I'd like for them to say: He took a few cups of love. He took one tablespoon of patience. One tablespoon, teaspoon of generosity. One pint of kindness. He took one quart of laughter. One pinch of concern. And then he mixed willingness with happiness. He added lots of faith. And he stirred it up well. Then he spread it over a span of a lifetime. And he served it to each and every deserving person he met." Muhammad Ali, when asked in 1972 how he'd like to be remembered

"They told me Joe Frazier was through,'' Ali told Frazier at one point during the fight.

"They lied,'' Frazier said before hitting Ali with a left hook.

The fight, which most in boxing agree was Ali's last great performance, was part of a 16-month period in the mid-1970s when Ali took his show on the road. He fought Foreman in Zaire, Frazier in the Philippines, Joe Bugner in Kuala Lumpur, Malaysia, and Jean Pierre Coopman in Puerto Rico. The world got a taste of Ali in splendid form with both his fists and his mouth.

In Malaysia, a member of the commission in charge of the gloves the fighters wore told Ali they would be held in a prison for safekeeping before the fight. "My gloves are going to jail,'' shouted a wide-eyed Ali. "They ain't done nothing -- yet!''

Ali went on to lose the title to Leon Spinks, then win it a third time on Sept. 15, 1978, when he scored a decision over Spinks in a rematch before 70,000 people at the Superdome in New Orleans.

Ali retired, only to come back and try to win the title for a fourth time against Larry Holmes on Oct. 2, 1980, at Caesars Palace in Las Vegas. Ali grew a mustache, pronounced himself "Dark Gable'' and got down to a svelte 217.5 pounds to try to beat Father Time. But Holmes, Ali's former sparring partner, mercifully toyed with him until Dundee refused to let Ali answer the bell for the 11th round.

"He was like a little baby after the first round,'' Holmes said. "I was throwing punches and missing just for the hell of it. I kept saying, 'Ali, why are you taking this?' He said, 'Shut up and fight. I'm going to knock you out.'"

When the fight was over, Holmes and his wife went upstairs to pay their respects to Ali. In a darkened room, Holmes told Ali that he loved him.

"Then why did you whip my ass like that?'' Ali replied.

A few years later, Ali said he would not have fought Holmes if he didn't think he could have won.

"If I had known Holmes was going to whip me and damage my brain, I would not have fought him,'' he said. "But losing to Holmes and being sick are not important in God's world.''

It was that world that Ali retreated to. He fought just once more and lost a 10-round decision to Trevor Berbick in the Bahamas.

Ali a World Beater Muhammad Ali fought in 12 countries over his 61 pro fights. His fights also extended over four continents ranging from North America, Europe, Asia and Africa for "The Rumble in the Jungle," when he fought and won against George Foreman in Zaire in 1974. Countries of Muhammad Ali's Fights Bahamas Canada England Germany Indonesia Ireland Japan Malaysia Philippines Switzerland United States Zaire -- ESPN Stats & Information

With wife Lonnie at his side, Ali traveled the world for Islam and other causes. In 1990, he went to Iraq on his own initiative to meet with Saddam Hussein, and he returned to the United States with 15 Americans who had been held hostage. One of the hostages recounted meeting Ali in Thomas Hauser's 1990 biography "Muhammad Ali -- His Life and Times.''

"I've always known that Muhammad Ali was a super sportsman, but during those hours that we were together, inside that enormous body, I saw an angel,'' hostage Harry Brill-Edwards said.

Ali served for 10 years as United Nations Messenger of Peace. In 2005, he won the Presidential Medal of Freedom, the nation's highest civilian award.

ESPN ranked Ali as the third greatest athlete of the 20th century, behind No. 1 Michael Jordan and Babe Ruth.

"We are sad to hear of the passing of Muhammad Ali. However, we revel in the memory of his athletic excellence in the ring, we recollect with pleasure the charm of the charismatic young man from Louisville who would shock the world, and we celebrate the dramatic achievement of a champion of civil rights who changed the world," ESPN president John Skipper said in a statement. "In many ways, he was truly the greatest of all time."

Tennis Hall of Famer and social activist Arthur Ashe summed up Ali's contribution to American race relations in an interview with Thomas Hauser.

"Ali didn't just change the image that African Americans have of themselves," Ashe said. "He opened the eyes of a lot of white people to the potential of African Americans, who we are and what we can be."

In a 1972 interview with David Frost, Ali was asked, "What would you like people to think about you when you're gone?"

Ali answered: "I'd like for them to say: He took a few cups of love. He took one tablespoon of patience. One tablespoon, teaspoon of generosity. One pint of kindness. He took one quart of laughter. One pinch of concern. And then he mixed willingness with happiness. He added lots of faith. And he stirred it up well. Then he spread it over a span of a lifetime. And he served it to each and every deserving person he met."

Information from The Associated Press was used in this report.