Muhammad Ali Dies: 'The Greatest' Boxer Dead at 74

— -- Three-time heavyweight champ Muhammad Ali, who charmed millions with his wit and confidence in the ring and inspired many more with his commitment to humanitarian causes died Friday, the family's spokesman said. He was 74.

"After a 32-year battle with Parkinson’s disease, Muhammad Ali has passed away at the age of 74. The three-time World Heavyweight Champion boxer died this evening,” said family spokesperson Bob Gunnell.

Ali was pronounced dead at 9:10 p.m. MT on Friday from "septic shock due to unspecified natural causes," Gunnell said on Saturday. His body was set to be returned to his hometown of Louisville, Kentucky, within the next 48 hours.

Ali's family will hold a private funeral service in Louisville, on Thursday, Gunnell said, with a public memorial service scheduled for 2 p.m. ET the following day. Former President Bill Clinton, sportscaster Bryant Gumbel and actor Billy Crystal were all set eulogize the late boxer at the service, which will also include a procession through the streets of Louisville.

"Muhammad's extraordinary boxing career only encompassed half of his life," Gunnell said at a press conference in Phoenix on Saturday. "The other half was committed to sharing a message of peace and inclusion with the world. Following his wishes, his funeral will reflect those principles and be a celebration open to everyone."

Ali had been hospitalized in the Phoenix area -- where he passed away -- for a respiratory issue June 2. At the time, a rep said he was in fair condition.

The late boxer's son, Asaad Ali, wrote on Instagram, "Forever grateful for everything you have ever gave me...You've shown me how to love the world in ways I didn't know possible."

His daughter Hana Ali tweeted, "Our father was a 'Humble Mountain!' And now he has gone home to God." Hana later posted a lengthier statement about Ali's passing, detailing the emotional final moments with her father.

"All of us were around him hugging and kissing him and holding his hands, chanting the Islamic prayer," she wrote in a statement posted on Twitter. "All of his organs failed but his HEART wouldn't stop beating. For 30 minutes...his heart just keep beating. No one had ever seen anything like it. A true testament to the strength of his Spirit and Will!"

One of the greatest fighters in the history of boxing, Ali retired in 1981 after losing to Trevor Berbick in his 61st career bout.

Soon thereafter, Ali -- who doctors said had begun showing signs of sluggishness and neurological damage in the 1970s -- began receiving treatment for Parkinson's disease.

Ali, who called himself "The Greatest," was married four times and had nine children, including daughter Laila, who also became a professional boxer. Ali and his fourth wife, Yolanda "Lonnie" Williams, had been married since 1986.

Muhammad Ali Through the Years in Photos

Read More About Muhammad Ali

Legendary Liston Bouts

Born Cassius Clay on Jan. 17, 1942, Ali first stepped in the ring at age 12 in his hometown of Louisville, Ky., after his bicycle was stolen and a police officer suggested he learn how to box. Ali went on to become one of the most successful athletes and revered public figures in history.

Acclaimed for his quick, dancing style as a fighter, Ali also blended a unique mix of political activism and personal conviction that won him international recognition outside of the ring.

After winning 100 of 108 amateur fights, Ali took home an Olympic gold medal at the 1960 Summer Olympics in Rome. He later allegedly chucked the medal into a river after a waitress at a soda fountain in Louisville refused to serve him because he was black.

Weeks after the Olympics, Ali signed a lucrative contract and won his first pro bout on Oct. 29, 1960, against Tunney Hunsaker. Ali quickly ingratiated himself with the media with his boastful claims and fresh, stylish way of speaking. He told Sports Illustrated in 1961: "Most of them [other boxers] … can fight almost as good as I can. I'm just saying you never heard of them. And the reason for that is because they cannot throw the jive. Cassius Clay is a boxer who can throw the jive better than anybody."

The brash, underdog Ali promised boxing fans he'd "float like a butterfly, sting like a bee" against Sonny Liston.

At age 22, he stunned the larger Liston, beating the champ in seven rounds in Miami to win his first heavyweight title. In their next match in 1965, Ali floored Liston with a hard, quick blow minutes into the bout and retained his crown when the referee stopped the fight.

Conscientious Objector Regains Fans, Titles

With one Olympic gold medal and a heavyweight belt to his credit, Ali soon began making headlines for his religious and political beliefs.

Inspired by black rights activist Malcolm X, he converted to Islam and changed his name to Muhammad Ali in 1964. When he refused in 1967 to serve in the U.S. Army because of his religious convictions, Ali fended off sharp criticism from a nation that was raw from the dividing forces of the Vietnam War and the civil rights movement. Ali was stripped of his heavyweight title in 1967, fined $10,000 and sentenced to five years in prison for draft evasion. That conviction was overturned by the U.S. Supreme Court in 1971.

Months later, Ali went head-to-head with Joe Frazier in a legendary 15-round fight. Frazier was unanimously declared the winner of the bruising bout and succeeded Ali as heavyweight champ. Ali said of the grueling fight, "It was like death. Closest thing to dyin' that I know of."