Penn State football coach Joe Paterno will retire at the end of the season, his long and illustrious career brought down because he failed to do all he could about an allegation of child sex abuse against a former assistant.

"This is a tragedy," Paterno said. "It is one of the great sorrows of my life. With the benefit of hindsight, I wish I had done more."

Paterno has been besieged by criticism since former defensive co-ordinator and one-time heir apparent Jerry Sandusky was charged over the weekend with molesting eight young boys between 1994 and 2009. Athletic director Tim Curley and vice-president Gary Schultz have been charged with failing to notify authorities after an eyewitness reported a 2002 assault.

The U.S. Education Department is investigating whether Penn State failed to report incidents of sexual abuse on campus, as required by federal law.

'Horrific mistake'

A sampling of reaction from Penn State players, coaches, alumni and others on Joe Paterno's decision to retire as coach after the season following child sex-abuse charges against former assistant Jerry Sandusky:

"It's really, really pulling on the emotions of the students. Right now, they don't know how to feel." — Penn State student body president T.J. Bard, a 20-year-old junior who says he's seen students in tears in the hallways.

"I think everybody makes mistakes and this is as horrific a mistake as has been made. … I think if the allegations are true, that everyone needs to be accountable because it's inexcusable." — Pittsburgh attorney Jon Perry, a 1997 graduate whose son, Alex, was accepted to Penn State's main campus on Tuesday.

"I love coach Paterno so am I emotional, yeah. People you love and care about, this is a hard thing for him, I'm sure. I know it is. So it hurts me when someone you love hurts. Other than that I have a job to do. I know he'd want me to do nothing else but take care of my team. — Rutgers coach and former Penn State assistant Greg Schiano.

"Shocked. It's not going to sink in yet. He's been a staple here for so long. It's kind of hard to realize there's going to be change." — Penn State junior Troy Weller, from Hatboro, Pa.

"Joe Paterno should step aside now and be happy that that's all he has to do!!" — Michael Strahan, former New York Giants defensive end and TV analyst, via Twitter.

"This one moment in time, this one decision, is going to tarnish his reputation and put a big black eye on Penn State and what he stood for. I can't imagine what it will be like to live with, knowing you knew this nine years go and you did the bare minimum. How many more lives were affected by that decision not to go topolice? How could he betray all of is like that?" — Penn State graduate Kathy Schmouder, 39, Selinsgrove, Pa.

— The Associated Press

Colleges and universities must report the number of crimes on campus and provide warnings if safety is threatened.

Paterno decided to retire at age 84, in the middle of his 46th season with the Nittany Lions. He won 409 games, a record for major college football, but now, the grandfatherly coach known as "Joe Pa," who had painstakingly burnished a reputation for winning "the right way," leaves the only school he's ever coached in disgrace.

"I am absolutely devastated by the developments in this case," he said. "I grieve for the children and their families, and I pray for their comfort and relief."

School could force Paterno's exit sooner

But Paterno might not be able to execute his exit strategy as the school's board of trustees is still considering its options, which could include forcing Paterno to leave immediately.

Paterno has not been accused of legal wrongdoing. But he has been assailed, in what the state police commissioner called a lapse of "moral responsibility," for not doing more to stop Sandusky, whose attorney maintains his client's innocence.

Paterno has been questioned over his apparent failure to follow up on a report of the 2002 incident, in which Sandusky allegedly sodomized a 10-year-old boy in the showers at the team's football complex. A witness, Mike McQueary, is currently receivers coach for the team but was a graduate assistant at the time.

Paterno told the athletic director, Tim Curley, who has since stepped down and has charged with lying to the state grand jury investigating the case. The Penn State vice-president has also been charged, and the university president could follow.

But in the place known as Happy Valley, none held the same status as Paterno. And in the end, he could not withstand the backlash from a scandal that goes well beyond the everyday stories of corruption in college sports.

"If this is true we were all fooled, along with scores of professionals trained in such things, and we grieve for the victims and their families," Paterno said Sunday, after the news broke, in a prepared statement. "They are in our prayers."

The coach defended his decision to take the news to his athletic director. Paterno said it was obvious that the graduate student was "distraught," but said the graduate student did not tell him about the "very specific actions" in the grand jury report.

After Paterno reported the incident to Curley, Sandusky was told to stay away from the school, but critics say the coach should have done more — tried to identify and help the victim, for example, or alerted authorities.

"Here we are again," John Salveson, former president of the Pennsylvania chapter of the Survivors Network of those Abused by Priests, said in an interview earlier this week. "When an institution discovers abuse of a kid, their first reaction was to protect the reputation of the institution and the perpetrator."

Paterno's requirement that his players not just achieve success but adhere to a moral code, that they win with honour, transcended his sport. Mike Krzyzewski, the Duke basketball coach, said in June for an ESPN special on Paterno: "Values are never compromised.

That's the bottom line."

Fans and detractors

His sudden departure leaves both his fans and detractors to ask who the real "Joe Pa" was.

Was he a gentle once-in-a-lifetime leader with a knack for moulding champions?

Or was he simply another gridiron pragmatist, a detached football CEO, his sense of right and wrong diluted by decades of coddling from "yes" men paid to make his problems disappear.

It will be a debate for years, and history will decide whether the enduring image will be that of Paterno surrounded by all those reporters as he hurried to practice this week, or his signature look on the sidelines.

Rolled-up khakis. Jet-black sneakers. Smoky, thick glasses. That famous Brooklyn accent that came off only as whiny as he wanted it to be.

"Deep down, I feel I've had an impact. I don't feel I've wasted my career," Paterno once said. "If I did, I would have gotten out a long time ago."

Along the road to the wins record, Paterno turned Penn State into one of the game's best-known programs, and the standard-bearer for U.S. college football success in the East.

National titles in 1982 and 1986 cemented him as one of the game's greats. In all, Paterno guided five teams to unbeaten, untied seasons, and he reached 300 wins faster than any other coach.

A year after he arrived at sleepy Penn State in 1966, Paterno began a 30-0-1 streak fuelled by players such as Jack Ham and Dennis Onkotz.

But the Nittany Lions fell short in the polls, finishing No. 2 in 1968 and 1969 despite 11-0 records, and No. 5 in 1973 despite a 12-0 record.

In 1969, Texas edged out Penn State for the title with help from an unlikely source: President Richard Nixon declared the Longhorns No. 1 after their bowl game.

"I'd like to know," Paterno later said, "how could the president know so little about Watergate in 1973, and so much about college football in 1969?"

Elite status finally arrived in the 1980s. The Nittany Lions claimed national titles in 1982, with a 27-23 win over Georgia at the Sugar Bowl, and in 1986, intercepting Miami's Vinny Testaverde five times in a 14-10 win at the Fiesta Bowl.

They have made several title runs since then, including the 2005 run to the Orange Bowl and an 11-1 regular-season campaign in 2008 that ended with a trip to the Rose Bowl and a 37-23 loss to Southern California.

"He will go down as the greatest football coach in the history of the game. Every young coach, in my opinion, can take a lesson from him," former Florida coach Urban Meyer said after his last game with the Gators, a 37-24 win over Penn State at the 2011 Outback Bowl.

Paterno's longevity became all the more remarkable as college football transformed into a big-money business.

The school estimated there have been at least 888 head coaching changes at FBS schools since Paterno took the job. He is the all-time leader in bowl appearances (37) and wins (24). And he sent more than 250 players to the NFL.

Paterno sets record

On Oct. 29, Penn State beat Illinois 10-7, earning Paterno win No. 409, breaking a tie with Grambling State's Eddie Robinson for most in Division I.

All he wanted to do, he had said two days earlier, was "hopefully have a little luck and have a little fun doing it. I've been lucky enough to be around some great athletes."

He said the success came because "the good Lord kept me healthy, not because I'm better than anybody else. It's because I've been around a lot longer than anybody else."

So long, in fact, that it seemed there was no getting rid of him, even as age and injuries crept up and his famous resistance to modern technology — tweeting, texting and other so-called must-haves of 21st century recruiting — turned him into a dinosaur.

But just as much, it was a string of mediocre seasons in the early 2000s that had fans wondering whether it was finally time for Paterno to step aside.

Others questioned how much actual work Paterno did in his later years. He always went out of his way to heap praise on his veteran assistants, especially if an injury help him from getting in a player's face in practice or demonstrating a technique.

"I'm not where I want to be, the blazing speed I used to have," he said in October, poking fun at himself. "It's been tough. …it's a pain in the neck, let me put it that way."