It was every parent’s worst nightmare.

Nearly three decades have passed, but John Walsh still can’t find the words to express the impact of his son’s abduction and murder. A successful businessman in Florida, Walsh was building luxury hotels; his $26 million resort dream project was under construction on Paradise Island, Bahamas. Then, on July 27, 1981, his 6-year-old son, Adam, disappeared during a shopping trip with his mother at a Sears department store in Hollywood, Fla.

In the weeks and months that followed, John Walsh couldn’t function. He lost 30 pounds. His life spiraled out of control. He and wife Revé were being suffocated by an unbearable, crushing grief. Fifteen days after the abduction, Adam’s severed head was found in a drainage canal 120 miles away from his home.

“It was the most heartbreaking, devastating event for us,” Walsh tells SUCCESS. “I don’t have the magic formula for how parents survive the murder of a child. Adam was a beautiful 6-year-old boy.”

But Walsh managed to do what most parents in his infernal situation can’t. He went from grieving father to grieving but gallant crusader, shaking the bitterness and becoming America’s most recognized advocate for victims of violent crime.

His turnaround began with a conversation with the Broward County medical examiner on the day he went to claim Adam’s remains at the morgue.

Walsh had previously spoken by phone with Dr. Ronald K. Wright shortly after Adam’s abduction. Wright encouraged Walsh to get the media involved in Adam’s case. He told Walsh there was no organized means of exchanging information across the country about unidentified dead people, especially children. Wright said most coroners in Florida simply exchanged information on a voluntary basis by mail or telephone. Adam’s remains could have been in a morgue somewhere at that very moment and nobody would know, Wright said.

John and Revé Walsh agreed to go national with their plight, traveling to New York to appear on Good Morning America with David Hartman. “We thought, ‘This is going to be the break because we’re going to show Adam’s picture nationwide,’ ” Walsh recalls. “We went up there and his remains were found that day—the worst day of our lives.”

The search for Adam had been the biggest of its kind in Florida history. Thousands of letters addressed to the Walsh home or to “Adam’s parents” or simply to “Adam, Hollywood, Fla.” arrived daily. But the outpouring of support did little to mend the Walshes’ shattered hearts. Revé patiently read the letters and stored them in the garage.

“Certainly, there were murdered kids before Adam, and we just were overwhelmed with these thousands of letters that were sent to our house,” Walsh says. “People with missing and runaway children and people who had been involved in divorces and their spouses had taken their child in an act of revenge.… People wanted to know what they could do.”

Walsh didn’t know where to turn until he called the medical examiner to request Adam’s remains for burial. When they met for the first time in person, the longtime medical examiner immediately started to swing away at the grief-stricken, 36-year-old Walsh. “We started talking, and he said, ‘You look terrible, and you look like you’re becoming a double victim.’ I said, ‘What does that mean?’ ” Walsh recalls.

“He said many crime victim survivors and families descend into hell and do terrible things. They get into drugs or alcohol to deal with the pain. There’s a huge ripple effect to violent crime, especially with a child. I told him I didn’t come to his office for a lecture or advice from him. I just wanted to get Adam’s remains.

“And he said, ‘Well, you look terrible, and you look like you’re contemplating suicide.’ I said that was none of his business, and, by the way, I asked, ‘What do I have to live for? I’ve lost my only son, my business is spiraling into hell and, again, I don’t want a lecture from you.’ ”

Wright reminded Walsh of the family, friends and supporters from around the state Walsh would disappoint if he “took the cowardly way out.”

Wright stressed that he believed in Walsh’s effectiveness as a communicator and as a person who could make a difference. “You either let it kill you, you let it break your heart and destroy you forever, or you try to make sure that Adam didn’t die in vain,” Walsh remembers Wright telling him.

“That conversation with Dr. Wright was my come-to-Jesus moment. I went home, and I stopped feeling sorry for myself.” From that moment on, John Walsh, now 64, set out to make sure his son did not die in vain.

He and Revé successfully pushed for creation of the Missing Children Act of 1982, initially written and introduced to Congress by U.S. Sen. Paula Hawkins of Florida, and the Missing Children’s Assistance Act of 1984. An average 2,100 children are reported missing each day, according to Justice Department statistics, and Walsh continues to testify before Congress and state legislatures on crime, missing children and victims’ rights issues.

The family also founded the nonprofit Adam Walsh Child Resource Center, and Walsh helped in successfully lobbying Congress to establish the National Center for Missing & Exploited Children (NCMEC) in 1984. This year marks the 25th anniversary of the two organizations’ merger.

As host since 1988 of the FOX network’s longest-running television series, America’s Most Wanted, Walsh has contributed to the capture of more than 1,000 fugitives, show executives say.

He also has been honored for his work by Presidents Ronald Reagan, George H.W. Bush, Bill Clinton and George W. Bush. On July 27, 2006—the 25th anniversary of Adam’s abduction— President George W. Bush signed The Adam Walsh Child Protection and Safety Act to track and apprehend convicted sex offenders who disappear after their release from prison.

In addition to being named “Man of the Year” by both the U.S. Marshals Service and the FBI, Walsh was also made an honorary U.S. marshal. He is only the third man to receive this honor in the organization’s 200-year history.

In October 2008, Walsh was awarded the Operation Kids 2008 Lifetime Achievement Award for his dedication to protecting children and to raising funds for the NCMEC.

“All of that grew out of that talk with Ronald Wright about trying to change the way that this country looked at missing, exploited, molested children,” Walsh says. “And the way the criminal justice system dealt with children, the way the justice system dealt with repeat sex offenders, and the lack of exchange of information, the lack of federal, state and local direction.”

Meanwhile, on Dec. 16, 2008, Adam Walsh’s murder investigation was closed. Officials named convicted serial killer Ottis Toole as the boy’s killer. Toole had confessed to the murder, but was never tried and, in 1996, died in prison at the age of 49.

Now living in Washington, D.C., with three children born following Adam’s death—Meghan, Callahan and Hayden— Walsh also credits Revé for his decision to become more involved and take control of his life.

Together, he says, they shared a “determination that this horrific act would not destroy us and that we would somehow have to come back to a place—not ever back to the same place— but back to a new place of respect and love and try to accomplish something together.”

Don Yaeger is a New York Times best-selling author, longtime associate editor at Sports Illustrated and nationally recognized motivational speaker.