Sanders was shot and killed in an armed robbery at a restaurant.
The shooting took place in Brits, near Pretoria, at a 21st birthday function for a family member on Saturday.
Sanders was wounded in the stomach and hand. He was taken to hospital, where he died of his wounds in the early hours of Sunday.
Corrie Sanders' second-round TKO win against Vladimir Klitschko on March 8, 2003 is one of the best-ever performances by a South African boxer.
Klitschko was considered the heir apparent to the great Lennox Lewis so Sanders' win was a great achievement, especially as Klitschko is back at the top again.
When the boxing websitepound4pound.com recently recalled Sanders' career, he was asked to describe his feeling of becoming champion of the world. Sanders replied: "It's the third best thing that happened to me in my life. The first and the second greatest things are my daughter and my son".
Tributes to Sanders have been pouring in on radio and on Twitter, as the boxing fraternity and the public hear of the shocking news.
Sports journalist Neal Collins says on his blog that Sanders was the victim of a random shooting when three armed men raided the restaurant at Thatch Haven Country Lodge, just off Carel de Wet Road near Brits outside Pretoria.
He died after emergency surgery at Kalafong Hospital.
"Corrie didn't try anything heroic, he was just in the wrong place at the wrong time. They shot him in the stomach. There was also a wound in his arm," an eyewitness told Collins.
"We were at Thatch Haven near Brits to celebrate with Corrie’s brother Mike. His son, also Mike, is 21 next week.
"There were 48 people at the restaurant, it’s just off the main road. We arrived at around 4pm on Saturday. At about 6pm, as it was getting dark, Mike gave a speech. Then the grandfather stood up and offered a prayer.
"That’s when we heard three or four shots. At first we thought it was the kids playing around. Then we realised it was serious.
"There were three of them. Armed with pistols. They were telling everyone to lie down and give them their wallets and mobile phones. They didn’t take much. They were working their way through the room when a car alarm went off outside and they panicked and ran.
"Corrie was the only one shot. He didn’t try anything heroic as far as I could see. He was just in the wrong place, by the entrance. They shot him through the stomach and I also saw a wound in his arm, it might have been from the same bullet, which went right through him.
"I think they shot him as a lesson to the rest of us, to say they were serious."
Olympic swimming champion Roland Schoeman expressed his shock on Twitter, saying "Can't describe in words how sad I am to hear about the senseless murder of my friend Corrie Sanders. RIP".
Recent Olympic gold medallist Cameron van der Burg, who along with Schoeman also hails from Pretoria - as did Sanders - said: “Rest in peace Corrie. A champion of the world”.
Former Springbok captain John Smith in London tweeted: "Just woke up to news of Corrie Sanders having been murdered last night, what another senseless waste of life in SA. RIP Champion".
Springbok rugby player Breyton Paulse tweeted “Gone too soon” while ex-Proteas cricketer Pat Symcox said: "Feel sick to the core. Just so damn angry over Corrie's murder. A helpless feeling and one that wants to scream out".
Former Bafana Bafana and Orlando Pirates star Mark Fish said: "So sad to hear about the tragic death of SA boxing great and a true gentleman Corrie Sanders. Condolences to all his family".
Sports reporter David Isaacson said: "Trainer Harold Volbrecht had a small gym: Corrie and Msukisi Sikali were stable-mates and world champs together. Both murdered. Shocking". Three-time world champ Sikali was killed in a stabbing in Uitenhage in 2005. He died for his cellphone.