Etan Patz's accused killer told investigators that he "wanted to let him go" but "something took over me," according to his videotaped confession to strangling the 6-year-old victim, which was played for the first time in court Monday.

Pedro Hernandez, 53, a former bodega worker from the SoHo neighborhood where Patz was last seen in 1979, said in the 2012 confession that he strangled the boy. His lawyer has challenged its reliability because his client has a history of mental illness and a low IQ.

During the interrogation, disclosed at a Manhattan court hearing on whether it was voluntary and whether police gave required warnings, Hernandez said he saw Patz -- on his way to school -- on the sidewalk, and lured him to the bodega basement by offering a soda.

"I grabbed him by the neck and started choking him," said Hernandez, speaking in a soft, meek voice and clutching his neck to illustrate. "I was nervous and my legs were shaking. I wanted to let go, and I couldn't let go. . . . I felt like something took over me."

He told investigators he kept squeezing until Patz went "limp" and dropped. He claimed the boy was still alive when he wrapped him in a garbage bag, stuffed it in a cardboard "banana box" and lugged it on his shoulder and dumped it in a nearby alley.

Hernandez estimated the entire episode took "three to four minutes." He insisted he never touched Patz sexually, but again and again deflected questions about his motives.

"I am sorry I did it," he said. "I wish there is something I could do to go back. . . . . Something was pushing me. Why I did it, I do not know."

Patz disappeared on the morning of May 25, 1979. His body was never found and the case was unsolved for 33 years. In 2012, amid publicity about the case, a tipster told police that Hernandez -- a married janitor living in Maple Shade, New Jersey, had privately admitted involvement.

He was charged with murder and kidnapping based on his confession. State Supreme Court Justice Maxwell Wiley ruled there was sufficient evidence of a crime to allow the case to proceed, but no forensic corroboration of Hernandez' confession has emerged.

Hernandez was picked up in New Jersey on May 23, 2012, and questioned for seven hours before making a taped confession, lawyers told Wiley. A second confession -- the one played in court -- was recorded in New York from 2 to 7 a.m.

Prosecutor Joan Illuzzi-Orbon told Wiley that Hernandez had ample time to rest during the day, and was calm and focused throughout the questioning. She said investigators first started to make progress when they asked him about abuse he suffered as a child.

Hernandez's lawyer, Harvey Fishbein, said the confessions should be thrown out because he didn't receive Miranda warnings for the first seven hours, was manipulated by police, and with an IQ of around 70, did not understand his right to remain silent. Fishbein said the confession was full of mistakes. Hernandez said he killed Patz on a sunny day, but it was cloudy, and claimed he threw Patz's book bag behind a bodega freezer, but it wasn't found by police during multiple searches in 1979, Fishbein said.

The hearing is expected to last up to a month. Wiley will decide whether the statements can be used in evidence. If he allows them, a jury will have to decide if it believes them.