Los Angeles ? Michael Jackson’s 50-concert comeback bid in London next month was intended to wash away the taint of freakish scandals and restore him to glory as the “King of Pop.” But the curtain will never rise.

In an instant Thursday, the man who moonwalked above the music world was gone, leaving a shot at redemption unfulfilled and fans and pop stars alike in anguish and shock.

“I can’t stop crying over the sad news,” Madonna said in a statement. “The world has lost one of the greats, but his music will live on forever.”

Said Dick Clark: “Of all the thousands of entertainers I have worked with, Michael was the most outstanding. Many have tried and will try to copy him, but his talent will never be matched.”

Jackson, 50, died at UCLA Medical Center after being stricken at his rented home in Holmby Hills. Paramedics tried to resuscitate him at his home for nearly three-quarters of an hour, then rushed him to the hospital, where doctors continued to work on him.

“It is believed he suffered cardiac arrest in his home. However, the cause of his death is unknown until results of the autopsy are known,” his brother Jermaine said. Police said they were investigating, standard procedure in high-profile cases.

Cardiac arrest is an abnormal heart rhythm that stops the heart from pumping blood to the body. It can occur after a heart attack or be caused by other heart problems.

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Jackson’s death brought a tragic end to a long, bizarre, sometimes farcical decline from his peak in the 1980s, when he was popular music’s premier all-around performer, a uniter of black and white music who shattered the race barrier on MTV, dominated the charts and dazzled even more on stage.

His 1982 album “Thriller” — which included the blockbuster hits “Beat It,” “Billie Jean” and “Thriller” — is the best-selling album of all time, with an estimated 50 million copies sold worldwide.

At the time of his death, Jackson was rehearsing hard for what was to be his greatest comeback: He was scheduled for an unprecedented 50 shows at a London arena, with the first set for July 13.

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The public first knew him as a boy in the late 1960s, when he was the precocious, spinning lead singer of the Jackson 5, the singing group he formed with his four older brothers out of Gary, Ind. Among their No. 1 hits were “I Want You Back,” “ABC” and “I’ll Be There.”

He was perhaps the most exciting performer of his generation, known for his backward-gliding moonwalk, his feverish, crotch-grabbing dance moves and his high-pitched singing, punctuated with squeals and titters. His single sequined glove, tight, military-style jacket and aviator sunglasses were trademarks, as was his ever-changing, surgically altered appearance.

Jackson ranked alongside Elvis Presley and the Beatles as the biggest pop sensations of all time. He united two of music’s biggest names when he was briefly married to Presley’s daughter, Lisa Marie, and Jackson’s death immediately evoked comparisons to that of Presley himself, who died at age 42 in 1977.

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As years went by, Jackson became an increasingly freakish figure — a middle-aged man-child weirdly out of touch with grown-up life. His skin became lighter, his nose narrower, and he spoke in a breathy, girlish voice. He often wore a germ mask while traveling, kept a pet chimpanzee named Bubbles as one of his closest companions, and surrounded himself with children at his Neverland ranch, a storybook playland filled with toys, rides and animals. The tabloids dubbed him “Wacko Jacko.”

“It seemed to me that his internal essence was at war with the norms of the world. It’s as if he was trying to defy gravity,” said Michael Levine, a Hollywood publicist who represented Jackson in the early 1990s.

Jackson caused a furor in 2002 when he playfully dangled his infant son, Prince Michael II, over a hotel balcony in Berlin while a throng of fans watched from below.

In 2005, he was cleared of charges he molested a 13-year-old cancer survivor at Neverland in 2003. He had been accused of plying the boy with alcohol and groping him, and of engaging in strange and inappropriate behavior with other children.

The case followed years of rumors about Jackson and young boys. In a TV documentary, he acknowledged sharing his bed with children, a practice he described as sweet and not at all sexual.

Despite the acquittal, the lurid allegations that came out in court took a fearsome toll on his career and image, and he fell into serious financial trouble.

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Michael Joseph Jackson was born Aug. 29, 1958, in Gary. He was 4 years old when he began singing with his brothers — Marlon, Jermaine, Jackie and Tito — in the Jackson 5. After his early success with bubblegum soul, he struck out on his own, generating innovative, explosive, unstoppable music.

Jackson married Lisa Marie Presley in 1994, and they divorced in 1996. Later that year, Jackson married Deborah Rowe, a former nurse for his dermatologist. They had two children together: Michael Joseph Jackson Jr., known as Prince Michael, and Paris Michael Katherine Jackson. Rowe filed for divorce in 1999.

Billboard magazine editorial director Bill Werde said Jackson’s star power was unmatched. “The world just lost the biggest pop star in history, no matter how you cut it,” Werde said. “He’s literally the king of pop.”

Jackson’s 13 No. 1 one hits on the Billboard charts put him behind only Presley, the Beatles and Mariah Carey, Werde said.

“He was on the eve of potentially redeeming his career a little bit,” he said. “People might have started to think of him again in a different light.”