(CNN) For years, a popular sports figure used his position of trust to sexually abuse vulnerable minors, all under the nose of a major state university. The public reckoning with that abuse forced out the university president and other leaders and set off extensive investigations.

Even as the case of Larry Nassar at Michigan State University continues to unfold, its similarities to that of Jerry Sandusky, who was arrested in 2011 for sexually abusing young boys at Penn State University and elsewhere, are striking. And they raise questions about how a seemingly parallel nightmare unfolded at Michigan State less than a decade after the Penn State saga.

Investigators' findings at Penn State led to the criminal convictions of Sandusky and top campus officials and tarnished the legacy of the university and its storied football program. Michigan State has denied any cover-up of Nassar's abuse. Still, the president and athletics director last month resigned amid pressure

For his part, Michigan State's attorney has rejected the Penn State comparison.

"Although both involve horrible actions by disturbed individuals -- Sandusky and Nassar -- the role of the University here is different," Patrick Fitzgerald wrote in December to Michigan's attorney general

"In the Penn State matter, it appears that high-ranking officials were aware of sexual abuse by an employee, decided to report the abuse to law enforcement, and then changed their minds and did not report the abuse," he wrote. "In the MSU matter, we believe the evidence will show that no MSU official believed that Nassar committed sexual abuse prior to newspaper reports in late summer 2016."

However, in both cases, experts told CNN, a series of textbook errors paved the way for crimes to be committed against children, their abusers jailed -- likely for life -- and intense scrutiny to fall upon university officials who were supposed to be keeping watch.

"There's no way to absolutely prevent an employee from doing something bad once," said Scott Berkowitz, board president and founder of the Rape, Abuse & Incest National Network . "But where the institutional breakdown comes is, once you start hearing allegations, doing little or nothing about it."

Here's a look at how the two situations compare.

Both perpetrators were revered, ...

Nassar, a team doctor for USA Gymnastics, became an associate professor at Michigan State in 1997, and he often treated young women affiliated with the school's sports teams. His work with the US women's Olympic gymnastics team made him a respected figure on campus, and several women said in court that he had a god-like status.

"My mom and I felt very lucky we were able to get an appointment at his office because of his exceptional reputation," Whitney Mergens said at Nassar's sentencing in a Michigan court in January.

Sandusky was the defensive coordinator for Penn State's football team for 23 years under legendary head coach Joe Paterno. He retired from coaching in 1999 and received emeritus status, so he had full access to the Penn State campus.

Sandusky also founded The Second Mile, a charity that helped troubled youth, some from broken homes.

Nassar's and Sandusky's respected positions in their communities helped shield them from critical oversight, Berkowitz said.

"It's always hard to believe a bad thing about someone you respect and admire," he said. "And that's true in the most private of cases, when it's a teacher or coach at a local school district."

... both preyed on vulnerable victims ...

Nassar used his status to systematically sexually abuse girls under the guise of providing medical treatment, he admitted in court.

More than 150 women told a Michigan court remarkably similar stories of him penetrating them with ungloved fingers during medical appointments.

Larry Nassar was sentenced in January to 40 to 175 years in prison after pleading guilty to seven counts of criminal sexual conduct in Ingham County, Michigan.

The majority of Nassar's victims were young teenagers. In addition, many were injured athletes looking for treatment and pain relief. What they got instead was sexual abuse.

Sandusky was convicted of sexually abusing at least 10 boys over 15 years, though similar allegations date to the 1970s.

Prosecutors cast Sandusky as a pedophile who preyed on victims using the charity he founded . Eight young men testified again him, often in disturbingly graphic detail, and described how Sandusky forced them to engage in sexual acts in places including the Penn State coaches' locker room showers, hotel rooms and the basement of his home.

"This is a case about a sexual predator who used his position within the university and community to repeatedly prey on young boys," Pennsylvania Attorney General Linda Kelly said of Sandusky in 2011

Predators seek out victims who are especially vulnerable, said Charol Shakeshaft, a professor at Virginia Commonwealth University and an expert on sexual abuse in schools.

"A predator looks for children who would be least likely to tell (authorities), and most likely to trust them or to be able to be talked into trusting them," she said. "That's how they choose."

... and after decades, both got caught.

Within a week of a September 2016 report by The Indianapolis Star detailing claims by Rachael Denhollander of abuse by Nassar , the physician was fired by Michigan State. Fifty more women in short order shared similar stories of abuse with Michigan State police and the state's attorney general, and Nassar was arrested and charged that November

Nassar pleaded guilty to seven charges of criminal sexual conduct in Ingham County, Michigan, and was sentenced in January to as many as 175 years in prison. He also was sentenced to 60 years in prison on federal child pornography charges, and he pleaded guilty to three other criminal sexual conduct charges in Eaton County, Michigan.

Nassar was "a monster that left me with more pain and scars than I came to his office with," gymnast Jade Capua said at Nassar's Ingham County sentencing

Sandusky was arrested in November 2011, more than two years after a Pennsylvania grand jury began investigating a 15-year-old's complaint to school and law enforcement authorities that the assistant coach had had inappropriate contact with him over four years starting when he was 10.

"The predator is going to be a predator," Shakeshaft said. "The people who can stop it is the bystanders. The people who see things happening, the people who hear a student complaining, ... if they're trained, they'll be able to help step up and stop it."

Staff failed to heed warnings ...

Several women said in court that they reported Nassar's abuse to Michigan State authorities but were dismissed or ignored.

Larissa Boyce said she and another accuser told Michigan State's head gymnastics coach Kathie Klages that Nassar had abused her. But rather than being protected, Boyce was "humiliated" and "brainwashed," she said in court.

"This could have stopped in 1997," Boyce said. "But instead of notifying authorities or even my parents, we were interrogated. We were led to believe we were misunderstanding a medical technique."

Klages retired last year after reportedly being suspended for defending Nassar . Her attorney, Steve Stapleton, told CNN his firm is representing her in federal civil litigation related to Nassar and won't comment on pending cases.

Other women who were abused by Nassar said they told other trainers or others at Michigan State but experienced similar pushback.

Michigan State ultimately sided with Nassar in the Title IX inquiry, concluding that his methods were medically appropriate. And, according to documents obtained by CNN, the university gave Nassar and Thomashow different versions of its investigative report, with hers devoid of a top school official's concerns about Nassar.

Meantime, at least 14 Michigan State University representatives received reports of sexual misconduct by Nassar in the 20 years leading up to his arrest, a Detroit News investigation found

At Penn State, several top administrators knew of allegations against Sandusky but didn't do enough to stop him, investigations have revealed

As early as 1976, one alleged victim told Paterno he'd been molested by Sandusky, court documents show . Paterno allegedly dismissed his report, saying, "I have a football season to worry about," the records show. Paterno and his family have denied his role in any cover-up.

Further, emails released in 2012 as part of Penn State's internal investigation show that in 2001, then-Penn State officials -- President Graham Spanier, Athletic Director Tim Curley and Vice President Gary Schultz -- discussed two alleged cases of abuse by Sandusky but didn't contact police.

One was a 1998 case in which a victim's mother filed a police report claiming her son had been inappropriately touched by Sandusky in the football locker room shower. The district attorney declined to prosecute.

The other case involved then-graduate assistant Mike McQueary's claim that he witnessed Sandusky in 2001 sexually abusing a boy in the football locker room showers. McQueary the following day reported the incident to Paterno, who told Curley and Schultz, then left the matter in their hands, Paterno and McQueary have said. Sandusky was convicted in 2012 in connection with the case.

Officials who receive such complaints should "investigate -- even if you don't have all the evidence you need in that first allegation," Berkowitz said.

"Take steps to prevent it," he said, "to lower the risk of it happening again."

Parents and kids, too, should be trained to recognize misconduct so they know to report a problem, Shakeshaft said.

"For kids, what should you look for? What should and shouldn't be happening? And for adults, what do you need to look for? If your child reports any of these things, report it to us immediately," she said.

... and faced their own repercussions.

Michigan State has acknowledged some process failures but has denied a deliberate cover-up of Nassar's abuse. No school officials face criminal charges.

special prosecutor also has been tasked with looking into "every corner" of Michigan State and how it responded to allegations against Nassar.

"You have to bear with us," attorney William Forsyth said upon his appointment. "This is almost 20 years of predatory conduct on the part of Nassar."

Meantime, Education Secretary Betsy DeVos has said her department would investigate, the NCAA has opened its own inquiry , and Michigan lawmakers want unredacted records of Michigan State's investigations of Nassar.

Sandusky's alleged pattern of abuse led to Spanier's and Paterno's firings days after the grand jury report's release in November 2011. Paterno died two months later at age 85.

Former FBI Director Louis Freeh later led Penn State's $6.5 million internal investigation, though his report is no longer available at the university's website.

"Four of the most powerful people at Penn State failed to protect against a child sexual predator harming children for over a decade," Freeh said in 2013, referring to Paterno and the three former campus leaders. Paterno's family slammed Freeh's report as "factually wrong."

Workers prepare to remove the statue of Penn State football coach Joe Paterno in 2012 in the wake of the Sandusky abuse scandal.

The key to any investigation into alleged crimes and a possible plot to hide them is its independence, experts told CNN.

"Just remember that a university's attorneys -- or any institution's attorneys -- are there to protect the institution, not to protect the child," Shakeshaft said. "So, you need outside examiners, you need an outside presence, because otherwise, the pressure is on to protect the institution, not the child."

Independent investigations also should be completely transparent to best serve the public's interest, Berkowitz said.

"Particularly a public institution like Michigan State," he said, "the public deserves to know what happened."