(CNN) -- The child sex investigation against retired Penn State defensive coordinator Jerry Sandusky began in 2008 with the first report of allegations to law enforcement. But allegations and eyewitness accounts, some known to university officials, date back as far as 1994.
Here's a look at the timeline, drawn from the grand jury report, the Pennslyvania attorney general's office and a statement from The Second Mile, a charity founded by Sandusky to help troubled youth:
1977 -- Sandusky founds "The Second Mile."
1994-1997 -- According to the grand jury report, Sandusky allegedly engages in inappropriate conduct with three different boys he met separately through the Second Mile program. One boy was 7 or 8, another was 10 and the third was 12 or 13 at the time. According to the grand jury report, the now-grown men said Sandusky engaged in inappropriate conduct ranging from touching to outright sexual encounters, including several incidents during the night before Penn State football home games, when the team, staff and boys Sandusky had allegedly invited were staying at a hotel.
1998 -- Penn State police and the Pennsylvania Department of Public Welfare investigate an incident in which the mother of an 11-year-old boy reported that Sandusky had showered with her son and may have had inappropriate conduct with him. In a June 1, 1998, interview with investigators from both agencies, Sandusky admits showering naked with the boy, admitting that it was wrong and promising not to do it again, according to the grand jury report. The district attorney advises investigators that no charges will be filed and the university police chief instructs that the case be closed, according to the testimony included in the grand jury report of the police detective who investigated the incident.
1999 -- Sandusky retires from Penn State after coaching there for 32 years, but stays on as a volunteer and retains full access to the campus and football facilities.
2000 -- Sandusky allegedly showers with a young boy and tries to touch his genitals during overnight stays at the coach's house, according to the now 24-year-old man's testimony included in the grand jury report.
2000 -- Tim Calhoun, a janitor at the Lasch Football Building on the Penn State campus, tells his supervisor and another janitor that he saw Sandusky performing oral sex on a young boy, according to the grand jury report. A second janitor reported that he saw Sandusky and a boy leave a shower room and walk out of the building hand in hand. No one reports the incident to university officials or law enforcement, according to the grand jury report.
March 2, 2002 -- According to the grand jury report, a graduate assistant allegedly tells Coach Joe Paterno that he saw Sandusky in the locker room shower the night before, performing anal sex on a young boy he estimated to be 10 years old.
March 3, 2002 -- Paterno reports the incident to Athletic Director Tim Curley, saying the graduate assistant had seen Sandusky "fondling or doing something of a sexual nature to a young boy," according to the grand jury. Later, the assistant is summoned to a meeting with Athletic Director Tim Curley and Senior Vice President for Finance and Business Gary Schultz..
While the assistant insists to the grand jury that he told Curley and Schultz that he saw Sandusky and the boy engaged in anal sex, Curley and Schultz told the grand jury they had not been told of such an allegation. Instead, Curley said he had the impression the conduct amounted to non-sexual "horsing around." Schultz said he couldn't remember details, but seemed to recall that "Sandusky might have inappropriately grabbed the young boy's genitals while wrestling," according to the grand jury. Sandusky's locker room keys are confiscated, he is told not to bring his Second Mile participants to campus and the incident is reported to the charity, but no law enforcement investigation is launched, according to the grand jury.
2002 -- The Second Mile learns of the shower incident. Curley tells them that "the information had been internally reviewed and that there was no finding of wrongdoing," the group said in a statement Monday.
2005 or 2006 -- Sandusky allegedly befriends another Second-Mile participant whose allegations would form the foundation of the multi-year grand jury investigation.
2006 or 2007 -- A wrestling coach at the high school where Sandusky was volunteering allegedly surprises Sandusky and the boy "lying on their sides, in physical contact, face to face on a mat" in a cramped weight room. Sandusky jumps to his feet and told the coach the two were just working on wrestling moves, the coach later recalls in grand jury testimony. As time goes on, Sandusky allegedly begins to spend more time with the boy, taking him to sporting events and giving him gifts, including golf clubs, a computer, cash and clothes. During this period, according to the grand jury report, Sandusky allegedly performs oral sex on the boy more than 20 times, and the boy performs oral sex on him once.
2008 -- The boy breaks off contact with Sandusky. Later, his mother calls the high school to report her son had been sexually assaulted and the principal bars Sandusky from campus and reports the incident to police. In grand jury testimony, the principal, Steven Turchetta, recalls Sandusky's behavior as suspicious, and said Sandusky was often "clingy" and "needy" when a student no longer wanted to spend time with him. The ensuing investigation reveals 118 calls from Sandusky's home and cell phone numbers to the boy's home.
November 2008 -- Sandusky informs The Second Mile that he is under investigation, and he is removed from all program activities involving children, according to the group.
September 2010 -- Sandusky retires from The Second Mile, according to the grand jury.
Friday -- The grand jury report is released.
Saturday -- Authorities arrest Sandusky on seven counts of involuntary deviate sexual intercourse and numerous other charges, including aggravated indecent assault, corruption of minors and endangering the welfare of a child. He is freed on $100,000 unsecured bail. Curley, 57, and Schultz, 62, are each charged with one count of felony perjury and one count of failure to report abuse allegations.
Sunday -- Curley asks for and is granted administrative leave to deal with the charges, while Schultz steps down from his post to retire.