NEW YORK (CNN) -- His was one of the first photos of a missing child to appear on a milk carton. Almost 30 years later, Etan Patz is still missing.

Etan Patz, who disappeared in 1979, was the first missing child featured in the milk carton campaigns of the 1980s.

Etan was 6 when he disappeared on May 25, 1979, the Friday before Memorial Day. He was on his way to school in what is now the upscale Soho neighborhood of New York.

It was the first time he'd walked to the bus stop by himself. It was just a few blocks away. Etan, like any 6-year-old, argued that all of his friends walked to the bus stop alone, and his parents relented.

His mother, Julie Patz, learned that Etan hadn't been in classes when he failed to return home. She called the school at 3:30 p.m., then called the homes of all his friends. When no one had seen Etan, she called police and filed a missing person's report.

By evening more than 100 police officers and searchers had gathered with bloodhounds. The search continued for weeks, but no clues to Etan's whereabouts were found. Watch an update on the case »

The boy's disappearance was one of the key events that inspired the missing children's movement, which raised awareness of child abductions and led to new ways to search for missing children. Etan's case was the first of the milk carton campaigns of the mid-1980s.

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"In our minds there were only two possibilities," said Stan Patz, the boy's father. "Either Etan was taken by a stranger and killed or he was taken by a very sad woman desperate for a child of her own, and we hoped that such a woman would at least take care of him and keep him safe."

Patz lived with this hope until 1982, when he learned of Jose Antonio Ramos' arrest and the surprising connection between him and a former babysitter of Etan's.

Ramos was a drifter who in 1979 lived in Alphabet City, a neighborhood not far from Soho. In 1982 he was arrested after boys in a neighborhood in the Bronx complained that he had stolen their book bags while trying to coax them into a drainpipe under a bridge, where he lived, said the Patzes and federal prosecutor Stuart GraBois, who spent years investigating the case.

When police found Ramos in his drainpipe home, they found he had many photographs of small blond boys. They noticed that they looked a lot like Etan Patz, according to author Lisa R Cohen's book about the case, "After Etan: The Missing Child Case that Held America Captive."

Bronx police questioned Ramos, and he denied having anything to do with Etan's disappearance. But he did tell police that his girlfriend used to baby-sit for the boy, GraBois said.

Prosecutors in the Bronx and Manhattan pursued this lead, but concluded they did not have enough evidence to connect Ramos to Etan's disappearance, GraBois and a spokesperson for the Manhattan District Attorney's Office said.

Ramos was released when the parents of the Bronx boys chose not to press charges against him, according to published reports. He left town and disappeared for six years -- until GraBois reviewed Etan's case. GraBois said he focused on Ramos as the prime suspect.

GraBois said he learned in 1988 that Ramos had been arrested and convicted of child molestation and was serving time in a Pennsylvania prison.

GraBois said he brought Ramos to New York for questioning and surprised him with the question: "How many times did you have sex with Etan Patz?"

Ramos told GraBois that he'd taken a little boy to an apartment he had on the lower East Side on the same day that Etan went missing. "He was 90 percent sure it was the same he'd seen in the news that was missing," GraBois said.

According to GraBois, Ramos claimed he released the boy and brought him to a subway station so the boy could go visit his aunt in Washington Heights.

"Etan did not have an aunt in Washington Heights," GraBois said. When questioned further, Ramos refused to say anything more and asked for a lawyer, according to GraBois.

Ramos is serving a 10- to 20-year prison sentence in Pennsylvania. He is scheduled to be released in November 2012, GraBois said.

GraBois said he had Ramos transferred to a federal prison, and planted informants as his cell mates. He wouldn't go into detail about what Ramos might have told them, but said he's convinced he's eyeing the right suspect.

GraBois turned over his evidence to the Manhattan District Attorney's Office, but prosecutors have not brought charges. They say that without a body, they don't have enough evidence.

Etan's case is still considered by the NYPD to be a cold case.

Anyone with information on the whereabouts of Etan Patz or that leads to the arrest and conviction of the individual responsible for his disappearance is asked to call the FBI/NYPD Etan Patz hotline: 212-384-2200.

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