CHICAGO — For months, federal authorities have hinted at the motive behind the hush-money payments former U.S. House Speaker Dennis Hastert has admitted to making: the sexual abuse of a teenage boy when Hastert was still a suburban high school teacher and wrestling coach in Illinois.

But now, a Tribune Newspapers investigation has uncovered new details of the case — at least four people have made what law enforcement sources say are credible allegations of sexual abuse against Hastert.

Tribune Newspapers has determined the identities of three of them, all men, whose allegations stretch over a decade when they were teenagers and Hastert was their coach.

One is dead. Tribune Newspapers has approached the other two — described in federal court records as Individuals A and D — and confirmed their roles in the case.

The man who received $1.7 million from Hastert and is at the center of the federal indictment— Individual A — declined to be interviewed. Behind the government's carefully worded court documents, reporters discovered a sometimes-pained narrative of his life since his days as a standout wrestler in the 1970s and how his interactions with Hastert might have affected him.

Individual D has talked to Tribune Newspapers at length but has not agreed to be named, although he is considering speaking at Hastert's sentencing in federal court April 27.

Tribune Newspapers typically does not name victims of alleged sexual abuse without their consent and is not doing so here.

Hastert is alleged to have sexually abused the teens when he was a teacher and coach at Yorkville High School, about 50 miles southwest of Chicago, decades before he became the longest-serving Republican speaker.

One of the alleged victims served as a team equipment manager a few years after Hastert arrived at the school in 1965.

Stephen Reinboldt died of AIDS in 1995, and Jolene Burdge, his younger sister, has long spoken out about the details she said he shared with her while alive.

Two others, who came to the school later, were talented and popular student-athletes from well-known local families — the sort of combination that often bodes well for the future. They all graduated from college.

The identity of the fourth accuser whom authorities have deemed credible remains unknown.

Now 74 and said to be in failing health after suffering a near-fatal blood infection and stroke, Hastert has not been charged with harming a child. Such charges, according to legal experts, would be barred by statutes of limitation. Instead, Hastert pleaded guilty last year to illegally structuring cash withdrawals to evade bank currency-reporting requirements as he pooled his money to give to Individual A as part of an agreement to keep him quiet.

Individual A: It was nearly one year ago that the indictment against Hastert was unsealed. Prosecutors said only that Hastert had skirted banking laws and lied to the FBI to conceal misconduct against Individual A, who has known Hastert much of his life.

Adding to Hastert's alleged betrayal, Individual A is a relative of one of the retired congressman's friends.

Hastert agreed during a 2010 meeting with Individual A to pay him $3.5 million in a financial agreement sources described as more akin to an agreed out-of-court settlement rather than extortion.

The sources confirmed Individual A's identity to Tribune Newspapers.

When Tribune Newspapers approached the middle-aged husband and father in February, Individual A said he didn't want to be rude but was “not interested” in speaking publicly and walked away. His wife acknowledged that her husband was a “victim.”

Hastert coached Individual A in the 1970s. A student leader, Individual A graduated from college, and when he applied for his first job in the mid-1980s, he listed Hastert as a reference.

He got the job, but left a short time later because of an anxiety disorder he described at the time as devastating.

He went on to work various jobs as he and his wife raised their family but fell deeper into debt. Court records show they had significant financial problems.

Individual A returned to his original profession, but he continued to struggle, providing another possible explanation for the financial arrangement with Hastert that was soon to begin. He pleaded guilty to misdemeanor drunken driving and was placed on 12 months' court supervision.

By March 2010, Individual A was on leave from his job for an undisclosed medical issue. He exhausted all of his paid time off by the end of the year and was terminated in 2011 after never coming back to work.

By then, he had begun receiving payments from Hastert.

By the time FBI agents questioned Hastert in December 2014 in his Plano, Ill., home, he had paid Individual A about $1.7 million, or about half the amount the two had agreed on.

Individual D: Tribune Newspapers spent 10 months contacting scores of athletes and students coached and taught by Hastert.

The man whom prosecutors recently publicly described as Individual D has spoken privately with Tribune Newspapers in a quest to learn more about the scope of the case.

The alleged misconduct against Individual D would have occurred late in the coach's tenure at Yorkville High School. Hastert left in 1981 after he won election to the Illinois Legislature.

A few years younger than Individual A, Individual D was a popular student and good athlete. He grew up to marry, have children and become a successful businessman. Prosecutors have said his decision to recently come forward has been a difficult one, and they have offered him the option of keeping his identity under seal in court records or appearing in court to read a victim-impact statement.

Prosecutors have recommended a sentence for Hastert ranging from probation to up to six months behind bars — the lowest possible sentence under federal guidelines for anyone convicted of a felony.

U.S. District Judge Thomas Durkin has noted that he is free to sentence Hastert to as long as five years in prison. AlthoughS the case has been shrouded in secrecy, the judge acknowledged for the first time during an unannounced court hearing last month about Individual D that it involved allegations of sexual abuse.

It was the second time in a week the judge had held a hearing in the case without any public disclosure in advance. The hearing became known only after Durkin posted an order announcing Hastert's sentencing date had been pushed back to accommodate Individual D's schedule, should he appear for the sentencing.

Hastert's attorneys, at least preliminarily, said they didn't plan to contest any facts alleged by Individual D, according to the transcript.

With the sentencing hearing looming, a source said Hastert called one of Individual D's relatives, hoping to get a letter to show Hastert had done good things with his life; that letter could help persuade Durkin to give Hastert a more lenient sentence.

Individual D then made a call of his own. He told federal authorities he would prepare a statement to be used in court detailing what Hastert did to him.

Tribune Newspapers' Jason Meisner contributed.

cmgutowski@tribpub.com