After 33 years of long waits and false starts, the investigation of Etan Patz's disappearance and the prosecution of the man who says he killed him moved with rapid force on Friday. Crime scene investigators swarmed the basement where the suspect, Pedro Hernandez, says he killed the boy; Mr. Hernandez was arraigned after being placed on a suicide watch; and new details emerged of his chilling confession - he told investigators he choked Etan moments after luring him to the basement. During Mr. Hernandez's first court appearance, his lawyer said his client had a history of mental illness that included hallucinations. Etan's father, Stanley, returned home to the same SoHo apartment where he and his wife, Julie, lived when their son disappeared exactly 33 years ago on Friday. Mr. Patz was mobbed by reporters but offered no comment. Meanwhile, the Police Department defended itself against suggestions that it had moved too quickly when it arrested Mr. Hernandez, a suspect with no known motive and with no physical evidence to corroborate his words. "There was no way we could release the man who had just confessed to having killed Etan Patz," said Paul J. Browne, the Police Department's chief spokesman. It would be unusual, to say the least, to release someone who confessed to a murder. The police have said Mr. Hernandez confessed to family members that he had killed a child, and on Friday, one of his sisters confirmed that account, saying in an interview that he had told them at a church prayer circle in the early 1980s. "He confessed that he killed a little boy," the sister, Norma Hernandez, said at her home in Camden, N.J. "He strangled a little boy and put him in the Dumpster." Asked why family members had not gone to the authorities then, the sister said they were torn. "They did not want to get involved because it was a brother," she said. Ms. Hernandez defended herself, saying her brother had never confessed to her, only to other relatives. "If he would have said something to me, he would be in jail," she said. She said Mr. Hernandez never told the relatives the name of the boy. But she recalled that when he moved to South Jersey from New York shortly after Etan disappeared, "He was acting very strange - he was always very quiet, his stomach was always very upset." Mr. Hernandez, 51, had started working as a stock boy at a bodega on West Broadway shortly before Etan vanished on the first day he walked by himself from his home on Prince Street to a school bus stop near the bodega. Mr. Hernandez's name was included in investigative files, revealing just how close the police had come to this suspect in the fraught weeks after Etan's disappearance. He told investigators this week that he had coaxed Etan away from the bus stop with the promise of a soda. By that time, shortly after 8 a.m., the bodega was already open, but the basement had a separate entrance from the sidewalk accessible by a set of metal doors. "He leads the kid down the steps to the basement and right there - at the bottom of the steps - he strangles him," one law enforcement official said. "He puts him in a bag, puts him in a box and carries it out," said the official, adding, "I don't think there is a passage of time" between when Mr. Hernandez strangled the boy and when he took the box out of the bodega. Mr. Hernandez said he took the box and dumped it a little over a block away in front of 113 Thompson Street, the police said, and on Friday night crime scene investigators had descended on that location. He was arraigned on Friday night on a charge of second-degree murder via a video feed from Bellevue Hospital Center to the courtroom of Judge Matthew A. Sciarrino Jr. of Manhattan Criminal Court. Mr. Hernandez had been taken to the hospital after he was placed on a suicide watch on Thursday night. The video showed him sitting at a table at Bellevue in an orange Correction Department outfit, his hands handcuffed behind his back, flanked by his lawyer and a court officer. Mr. Hernandez, who had a mustache, a goatee and close-cropped hair, did not move or react noticeably during the brief proceeding. Reporting was contributed by Al Baker, Anne Barnard, Russ Buettner, Alison Leigh Cowan, Alain Delaquérière, Joseph Goldstein, Randy Leonard, Nate Schweber and Kirk Semple.