His last known appearance was at a Parkinson's fundraiser April 9 in Phoenix, according to the Arizona Republic.
At the annual fundraising event for the Muhammad Ali Parkinson Center at Barrow Neurological Institute, one of the most recognizable faces on the planet was shielded in part by dark sunglasses, according to a photo posted by the newspaper.
Ali had missed the gala the previous two years, the newspaper reported. On that April night, however, one of the most beloved athletes of all time would receive a final standing ovation.
Ali's last battle
On Monday, the charismatic former boxer became ill with what family spokesman Bob Gunnell described as a respiratory issue.
He was admitted to the HonorHealth Scottsdale Osborn Medical Center in Scottsdale in fair condition that night.
"We expected that to be the case," Gunnell told reporters Saturday. "You know, Muhammad has battled back many times. We expected it to happen this time."
Ali also was hospitalized in January 2015 with a urinary tract infection. He was hospitalized in December 2014 with pneumonia.
"When he came into the hospital, we thought, 'OK, it will be a brief stay,'" said longtime friend John Ramsey, who works for WAVE in Louisville, Kentucky -- Ali's hometown -- and who has a radio show on ESPN.
'Wasn't going to improve'
Ali's condition worsened in recent days, according to Gunnell.
"The family was called when things became more serious," the spokesman said. "We still had a lot of hope it was going to turn around."
Two days ago, doctors told Ali's wife, Lonnie, that "his condition wasn't going to improve," Gunnell said.
Ramsey said Lonnie Ali called him Friday morning. Her husband's health was deteriorating.
"She said, 'You might want to come out,' which I decided to do," he said.
Surrounded by his children
Ali's daughter, Hana, wrote in a tweet that Ali was surrounded by his children in his final moments. They held his once powerful hands. They hugged and kissed their 74-year-old father. They chanted Islamic prayer.
Hanna Ali wrote that the children tried to stay strong. Some whispered in his ear.
"You can go now. We will be okay. We love you. Thank you. You can go back to God now."
After Ali's organs failed, his daughter wrote in the tweet, his heart continued to beat for another 30 minutes: "A true testament to the strength of his Spirit and Will!"
Ali died Friday night at 9:10 MT, the result of septic shock due to unspecified natural causes, Gunnell said. "He did not suffer."
His family was with him during his final 24 hours, Gunnell said.
"They got to spend quality time with him to say their final goodbyes, and it was a very solemn moment," he said.
"It was a really beautiful thing to watch because it displayed all that is good about Muhammad Ali... The champ would have been very proud of his family."
'Daddy is free now'
"Our hearts are literally hurting," Hana Ali wrote on Twitter. "But We are so happy daddy is free now."
Another daughter, Maryum Ali, said in an email to CNN's Jason Carroll: "I am happy my father no longer struggles. He is in a better place. God is the greatest."
Ramsey said he didn't actually see Ali in the hospital. The people who were with Ali were "the kids, family only, and I respected that... it's a very private matter."
Gunnell said many of Ali's closest friends flew in to be with the family. But they waited outside the hospital room out of respect for the family's privacy.
"It's very rough at this point," Gunnell said of the Alis. "All family members are having a tough time."
'Only one hometown'
Ali's life will be celebrated in his Kentucky hometown with ceremonies on Thursday and Friday.
Three off-duty Louisville police officers will escort his bodyto Kentucky, according to police spokeswoman Alicia Smiley.
Ali's family also will accompany the body.
"Muhammad Ali belongs to the world, but he only has one hometown," Louisville Mayor Greg Fischer said at a ceremony Saturday.
"The 'Louisville Lip' spoke to everyone, but we heard him in a way no one else could -- as our brother, our uncle, and our inspiration."
A public memorial is scheduled for Friday at 2 p.m. ET at the Yum Center, a basketball arena in the city where Ali grew up and began his amateur career as a 12-year-old.
'The people's champion'
Former President Bill Clinton, longtime sportscaster Bryant Gumbel and comedian and close Ali friend Billy Crystal will be among those delivering eulogies.
The immediate family will have a private gathering Thursday. They released a statement Saturday.
"Muhammad Ali was truly the people's champion and the celebration will reflect his devotion to people of all races, religions and backgrounds. Muhammad's extraordinary boxing career only encompassed half of his life. 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."
Before the service, Ali's body will be driven through the streets of Louisville. He will be interred at Cave Hill Cemetery.