(CNN) -- A day after Pedro Hernandez was charged in the killing of 6-year-old Etan Patz, prosecutors now face the task of corroborating his confession and piecing together a mystery that's confounded investigators for more than three decades.
Police say the 51-year-old New Jersey resident confessed to strangling Etan and dumping his body in the trash near a Manhattan bodega where he worked as a teenage stock clerk in 1979.
Attorney Harvey Fishbein said Hernandez -- who is currently on suicide watch at Bellevue Hospital -- has not entered a plea due to a pending psychiatric evaluation.
Fishbein says his client has a "long psychiatric history" including schizophrenia, bipolar disorder and hallucinations.
New York Police Commissioner Ray Kelly said earlier this week that authorities interviewed other employees of the store Hernandez worked at, but not him. "I can't tell you why," Kelly said.
Yet two law enforcement sources said Hernandez was in fact interviewed, albeit briefly. A third source said Hernandez not only talked to police, but he confessed -- though he was ruled out as a suspect, because his claims weren't believed.
At a recent news conference announcing Hernandez' arrest, Kelly said Hernandez had no prior contact with the boy, and that investigators have not uncovered any forensic evidence linking Hernandez to the disappearance of the Etan, whose body still has not been found.
Former SoHo resident Roberto Monticello, who says he knew Hernandez at the time of Etan's disappearance, called the former stock clerk a "very strange guy."
"He was always by himself," Monticello recalled to CNN affiliate NY1. "(I) never saw him with people."
His pastor, George Bowen, described Hernandez as a "very quiet, unassuming, almost shy man," attending church regularly with his wife and daughter, and sitting in the same seat almost every Sunday.
"So every Sunday morning I had a conversation with him," Bowen told CNN Saturday. "But the conversation was more or less a greeting."
One of the suspect's sisters told The New York Times that some family members claimed he had told them about the alleged murder in the early 1980s.
"He confessed that he killed a little boy," Norma Hernandez told the Times, saying that the suspect had moved to southern New Jersey shortly after Etan disappeared.
But she said that he had never told her directly and never mentioned the boy's name.
Norma Hernandez, according to the newspaper, said that her family had been torn over whether to inform authorities after the confession, but ultimately did not.
"They did not want to get involved because it was a brother," she told The Times.
Lisa Cohen, whose 2009 book, "After Etan," is widely considered the definitive account of the case, said Saturday that she remains skeptical about the man's confession.
"I had never heard of Pedro Hernandez before this week," she told CNN.
Etan went missing on May 25, 1979, a block from his home in Manhattan after walking to a school bus alone for the first time.
His disappearance helped spawn a national movement to raise awareness of missing children, including the then-novel approach of putting an image of the child's face on thousands of milk cartons.
The tipster whose information led to Hernandez's arrest contacted authorities last month after news coverage of their renewed search. That contact, at least in part, prompted investigators to question Hernandez.
Police Commissioner Kelly said earlier this week described Hernandez's actions as a crime of opportunity and said the suspect was remorseful.
"The detectives thought (the confession) was a feeling of relief on his part," Kelly said.
After that confession, investigators spent two days talking to witnesses and looking for anyone who could discredit Hernandez and couldn't find any, according to a source with knowledge of the case.
Manhattan District Attorney Cy Vance ultimately gave the green light to file murder charges against Hernandez based largely on his confession, even given the lack of physical evidence and questions about his mental state, the source said.
The next major step in the legal process would be for a grand jury to hear prosecutors' evidence against Hernandez for a potential indictment, after the defense waived its right to an expedited indictment on Friday. It is not clear when this might happen.
Etan was officially declared dead in 2001 as part of a lawsuit filed by his family against Jose Antonio Ramos, a drifter and convicted child molester acquainted with Etan's babysitter.
A judge found Ramos responsible for the boy's death and ordered him to pay the family $2 million, money the Patz family has never received.
Although Ramos was considered a key focus of the investigation for years, he has never been charged in the case. He is serving a 20-year prison sentence in Pennsylvania for molesting another boy and is set to be released this year.