Updated

He claims he killed Etan Patz, but when the man accused of the murder last saw the missing child, the boy was still breathing, according to new details about the confession.

Pedro Hernandez — who was an 18-year-old SoHo bodega clerk when Etan Patz, 6, vanished near the store in 1979 — told cops he "placed the boy in a plastic bag [and] placed the bag in a cardboard box," according to defense papers filed in Manhattan Supreme Court yesterday.

"He then carried the box to the entranceway of a basement approximately one-and-a-half blocks away, where he placed the box on the ground just inside the open entranceway," the papers say.

Hernandez's confession was taped in May at the Camden County, NJ, prosecutor's office, near his current home in Mount Holly.

"According to the video-recorded statement by Mr. Hernandez, when he left the box, Etan Patz was still alive," the papers say.

A law-enforcement source who asked not to be identified told the Post that Hernandez said that although Etan was breathing, he was motionless.

"He said [Etan] was unconscious, but still breathing. He was almost dead," said the source. "Hernandez said he panicked and dumped the body."

It was some seven to eight hours after he was taken into custody that Hernandez, who has an IQ of approximately 70, made that first video-recorded statement to cops, his lawyer, Harvey Fishbein, told reporters after his client pleaded not guilty to kidnapping and murder charges.

In a second videotaped statement, made the next day at the Manhattan DA's Office, Hernandez added that “Etan Patz might have died because of his [Hernandez’s] actions,” the papers said.

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