STATE COLLEGE — Jerry Sandusky's son told police he was sexually abused starting when he was 8, a decade before the former Penn State assistant football coach adopted him, according to a police interview recording obtained by NBC News.

Matt Sandusky, who was adopted by Jerry Sandusky as an adult, described for investigators showering with the ex-coach and trying to avoid being groped in bed. He also said he was undergoing therapy, that his memories of abuse were only now surfacing and that he was coming forward so his family would know what happened.

"If you were pretending you were asleep and you were touched or rubbed in some way you could just act like you were rolling over in your sleep, so that you could change positions," the now-33-year-old Matt Sandusky said in an excerpt played Tuesday on NBC's "Today."

His attorneys confirmed the recording's authenticity to The Associated Press.

"Although the tape was released without Matt's knowledge or permission, it illustrates that he made the difficult decision to come forward and tell the painful truth to investigators despite extraordinary pressure to support his father," lawyers Justine Andronici and Andrew Shubin wrote in a statement.

The same lawyers issued a statement Thursday saying Matt Sandusky had been abused and had spoken to investigators during his father's trial. The next day, Jerry Sandusky was convicted on 45 criminal counts stemming from the abuse of 10 boys, all of whom he met through his charity for at-risk youth, The Second Mile.

Matt Sandusky met the man who would eventually adopt him through the same organization.

Jerry Sandusky, who has five other adopted children, hasn't been charged with abusing his son.

Matt Sandusky sat with the ex-coach's wife, Dottie, on the first day of the trial, but left after hearing one of the accusers testify. His attorneys have said he reached out to them while the trial was under way, saying he wanted to talk to prosecutors.

Messages left for Sandusky's other children were not returned.

On the police recording, Matt Sandusky says he was sexually abused off and on between the ages of 8 and 15. While being questioned by an investigator, he says Jerry Sandusky would blow raspberries on his stomach and touch his genitals.

Those acts were similar to ones described by other victims who testified against Sandusky.

One of the accusers also said Matt Sandusky was living at the Sandusky home at the time he stayed there overnight and testified that Jerry Sandusky came into the shower with the two boys and "started pumping his hand full of soap." Matt Sandusky shut off the shower and left, appearing nervous, the witness said.

In the recorded interview, Matt Sandusky was asked if he recalled engaging in oral sex or being raped by the former Penn State coach, Matt Sandusky says "at this point I don't recall that."

He is heard on the tapes as saying that he had tried to escape from Sandusky and also had attempted suicide at one point.

"I know that I really wanted to die at that point in time," he said.

Matt Sandusky's abuse allegations date as far back as the late 1980s, about a decade before the allegations on which Jerry Sandusky was tried.

Last week, Travis Weaver, now 30, told NBC he was abused by Sandusky as early as 1992. His lawyer, Jeff Anderson, said he represents more Sandusky victims that have not yet gone public.

The attorney general's office declined to comment about Matt Sandusky's claims or whether they would result in more charges. Attorney General Linda Kelly has maintained that the investigation into Sandusky is ongoing.

Matt Sandusky was prepared to testify against his father, lawyers have said. Defense attorney Joe Amendola has said that prosecutors told the defense that if Jerry Sandusky took the stand, Matt Sandusky would have been called as a rebuttal witness.

Another defense attorney, Karl Rominger, told the AP he and Amendola heard the tape before deciding not to put Jerry Sandusky on the stand.

He said that Matt Sandusky, on the tape, makes "allegations that directly contradicts sworn testimony .... directly contradicts police statements he'd given previously, directly contradicts public statements and absolutely contradicts everything his family knows."

A message seeking comment from Amendola was left by AP on Tuesday at his office.

Afterward, Judge John Cleland issued an order prohibiting the defense attorneys from disclosing any material given to them by prosecutors that was not introduced at trial. It also gave Sandusky's attorneys 10 days to provide the court with an inventory of all discovery materials that were distributed to any member of the defense team or other person.

Explaining why he decided to come forward after publicly standing by his dad, Matt Sandusky said it was for his family, "so that they can really have closure and see what the truth actually is. And just to right the wrong, honestly, of going to the grand jury and lying."

Jerry Sandusky, 68, is under observation at the Centre County jail, where he is being kept away from other inmates pending a psychological review that will help determine the next step toward his sentencing in about three months.

Rominger said Sandusky is adamant about his innocence.

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Pennell contributed to this story from Philadelphia.