Jerry Sandusky's writings in a 2000 memoir about the difficult relationship with his adopted son, Matt, are similar to several letters he wrote to a boy now known as alleged victim No. 4.

Matt Sandusky, now 33, came forward this week as his father's child-sex trial drew to a close to say he, too, had been molested by Jerry Sandusky and was willing to testify.

Matt, like No. 4 and many other of Sandusky's accusers, got to know the former Penn State defensive coordinator through The Second Mile charity Sandusky founded in 1977 for at-risk kids.

No. 4, the first of eight alleged victims to take the stand in Sandusky's trial, mentioned Matt in his testimony, describing an awkward moment in the showers with the boy and his father.

"One time (Sandusky) and me and his son, Matt, had gone to play racket ball," No. 4 recalled. "Matt went into the shower, and then me and Jerry came in. (Jerry) started pumping his hand full of soap, like he was going to throw it. Matt got out, he went to another shower." The witness was asked to describe Matt's expression.

"Nervous," he said.

The exchange raised eyebrows in the courtroom, but soon was lost in an avalanche of dramatic testimony.

Sandusky's relationships with both boys followed a familiar pattern, according to testimony and the memoir. They began as rescue missions, expectations were raised, and then they crumbled in disappointment and estrangement.

The letters written by Jerry Sandusky to No. 4 are in the jury's hands and may well hold the key to some of the most serious charges against him.

In the letters, he sometimes assumed the voice of a mentor, providing words of inspiration and encouragement. But he could also appear needy, scolding and manipulative.

At times, he sounded like a love-struck teenager weathering that first painful breakup.

Judge John Cleland allowed reporters to view copies of the letters and other trial exhibits on a big screen in the courtroom after the jury retired for deliberations. Only parts of the letters had been read aloud during the trial.

Sandusky, 68, is charged with 48 counts and accused of molesting 10 boys over 15 years. He has denied the charges but did not take the stand at his seven-day trial.

Prosecutor Joseph McGettigan alleges Sandusky used The Second Mile to troll for preteen boys to molest. He called Sandusky "the perfect predatory pedophile," saying he groomed victims for sexual encounters in Penn State's locker room showers, hotel rooms and a waterbed in the basement of his home.

CNN does not disclose the names of alleged sexual assault victims; Matt Sandusky's name is being used because he made it public through his attorneys.

"This has been an extremely painful experience for Matt," his lawyers, Andrew Shubin and Justine Andronici, said in making the announcement about Matt's allegations. The lawyers also represent two other Sandusky accusers, referred to in court records as alleged victims No. 3 and No. 7.

In "Touched: The Jerry Sandusky Story," Sandusky wrote that Matt was 7 or 8 when he showed up at The Second Mile. He said the boy "became an instant challenge for me."

As with the boys who testified at his trial, Sandusky began as a mentor and father figure to Matt -- and then the relationship intensified and ultimately soured, according to the book. Sandusky became Matt's foster parent, and then his adoptive parent.

For a while, Sandusky says in the book, Matt turned his life around, but the relationship between the two has been strained in recent years. Matt has had his share of troubles.

According to court records cited by the Harrisburg Patriot-News, Matt Heichel, as he was then known, left the home he shared with his mother, brother and sisters to live in foster care with the Sanduskys when he was 11. But Matt attempted suicide a few months after moving in with the Sanduskys. He also ran away from the Sandusky home and was accused of stealing.