Dec. 16, 2008 -- A drifter who died in prison 12 years ago was responsible for the 1981 abduction and murder of Adam Walsh, bringing to an end one of the country's most famous cold cases, police in Florida announced today.

The six-year-old son of "America's Most Wanted" host John Walsh went missing from a Hollywood, Fla., mall more than 27 years ago. His head was discovered two weeks later, though his body was never found.

Hollywood, Fla., police named Ottis Toole, a convicted killer long suspected of the Walsh murder, who died in prison in 1996, as the perpetrator.

"For 27 years we've been asking who could take a six-year-old boy and murder him and decapitate him? Who? We needed to know," said John Walsh, as tears streamed down his face. "And today we know. The not knowing has been a torture but that journey is over."

Hollywood Police Chief Chadwick Wagner apologized to the Walshes for mistakes that he said were made early on in the investigation, before he became police chief, saying there was enough evidence against Toole to charge him before his death.

Wagner said there was no new evidence against Toole that made police name him as the killer, but that there was a "vast amount" of circumstantial evidence. "If Ottis Toole were alive today, he would be arrested for the abduction and murder of Adam Walsh," he said.

"What was there was everything that was in front of our face for years," he said. "This case could have been closed years ago."

From Ordinary Father to 'America's Most Wanted'

The murder transformed John Walsh's life, turning him from a middle-class hotel marketing executive into one of country's best known advocates for missing children.

"The not knowing is almost as bad as the murder but today's a good day. Today's a wonderful day," Walsh said today. "We can end the chapter of our lives. For all other victims who haven't gotten justice, I say one thing, don't give up hope. Don't give up hope."

After his son's death, Walsh, who will turn 63 later this month, became a tireless advocate for missing children. He started the Adam Walsh Child Resource Center and co-founded the National Center for Missing and Exploited Children. His television show, "America's Most Wanted," debuted in 1988.

Since 1984, the center has assisted law enforcement with more than 148,160 missing child cases, resulting in the recovery of more than 132,300 children.

"America's Most Wanted" went on to become one of the country's longest-running television shows. It began profiling missing persons, especially children, in 1991. It was briefly canceled in 1996, but reappeared after a public outcry. The show says its reports have led to the capture of more than 1,000 fugitives.

"We were absolutely devastated, heartbroken," Walsh told Larry King on the 25th anniversary of his son's abduction. "We had nothing in common but the anger and the grief. And [Walsh's wife, Reve] said, 'You know, we're destroying ourselves. This is not something that Adam would want. We've forgotten who the real victim is.'"

The Walshes lobbied for the Missing Children Act, which was passed in 1982 and set up an FBI database of missing children. In 2006, President Bush signed the Adam Walsh Child Protection and Safety Act, which, among other things, created more stringent requirements for sex offender registration.

Adam Walsh's Mysterious Disappearance

On July 27, 1981, Reve Walsh went with her son to the Sears department store in the Hollywood mall. She left him in the toy department playing video games. When she returned a few minutes later, he was gone. They never saw each other again.

Toole: Adam Walsh's Killer

The police, without the benefit of the missing children search tools that Walsh would later champion and modern tracking systems, were overwhelmed. "Leads are coming in and nobody's looking at them. And people are throwing them around. And I, I saw one on a napkin, I saw one here, I said, you know, there's no organization," Joe Matthews, a Miami Beach homicide detective, told ABC's Primetime in 2007.

The names of numerous possible suspects have been advanced over the years, including Jeffrey Dahmer.

Toole, a serial killer who was in prison for an unrelated murder, twice admitted to killing Adam, but recanted both times. Toole, the partner of notorious serial killer Henry Lee Lucas, reportedly confessed to committing dozens of murders, though many of those claims later proved to be false.

Police were unable to find Walsh's body in the area where Toole said it was located. During his first confession, in 1983, Toole reportedly said he used a machete to cut off Adam's head.

Police recovered a bloody piece of carpeting from Toole's car, but with no sophisticated DNA testing available at the time, police could never determine if it contained Adam Walsh's blood. The carpeting later disappeared.

Documents released Tuesday show that detectives who reexamined the case in 1996 located several people who were at the Hollywood mall on the day Walsh was abducted but who had not been shown a photo lineup during the original investigation.

Several of those witnesses said they saw Toole at the mall; one witness said he had seen Toole talking to Walsh, the documents say.

ABC News' Jason Ryan and Geoff Martz contributed to this report.