PEOPLE Explains: Everything to Know About Ex-Gymnastics Doctor Larry Nassar's Sex Abuse Case

Former Team USA gymnastics doctor Larry Nassar was sentenced on Wednesday to up to 175 years in prison for sexually abusing women and girls for decades during his time at Michigan State University and as a team USA Gymnastics doctor.

The world watched Wednesday afternoon as Judge Rosemarie Aquilina of Michigan’s Ingham County Circuit Court sentenced the 54-year-old predator to the lengthy sentence — after the court heard moving impact statements from dozens of victims.

“I just signed your death warrant,” Aquilina said after announcing the prison terms. “As much as it was my honor and privilege to hear the sister survivors, it is my honor and privilege to sentence you. Because, sir, you do not deserve to walk outside of a prison ever again.”

The final day of the powerful hearing was the culmination of a years-long effort to take down the abuser. More than 150 women and girls have accused Nassar of assault, including gymnasts Aly Raisman, Simone Biles, McKayla Maroney and Gabby Douglas. Nassar pleaded guilty in November to several counts of first-degree criminal sexual conduct.

“We know without a doubt after these seven days — what we and this team have known for 16 months — [Nassar] is perhaps the most prolific child molester in history … who spared no one,” Assistant District Attorney Angela Povilaitis said in court on Wednesday.

Here is everything you need to know about the headline-making trial:

Allegations of Nassar’s Abuse Became Public in 2016

In August 2016, the Indianapolis Star published findings from its ongoing investigation into sexual abuse inside USA Gymnastics, the governing body for the U.S. Olympic team. The investigative team found that organization officials failed to address allegations of sexual abuse. Shortly after, Nassar was reassigned from all clinical duties at Michigan State University. He was fired from the school in September 2016.

He was fired by USA Gymnastics a year earlier, in 2015, after working with the organization since 1986, and served as national medical coordinator since 1996, The New York Times reported.

Rachael Denhollander and Another Unnamed Former Gymnast Were the First to Speak Out

In September 2016, Denhollander and another woman revealed to the Indianapolis Star that Nassar molested them during multiple treatments in the 1990s and early 2000s. They said that Nassar fondled them and spoke about oral sex when they were alone, according to the publication. Both filed a lawsuit or complaint as a result of the abuse.

She said she went to Nassar as a child about pain, adding that he molested her with her mother in the room.

“As he was doing that, he also began to massage internally,” she said. “My mom was actually in the room at the time and he would just position me and position myself so that she couldn’t see what he was doing.”

He Has Faced Sex Abuse and Child Pornography Charges

Last month, Nassar was sentenced to 60 years in prison for possessing thousands of images of child pornography, according to the Lansing State Journal and other outlets. Those charges are unrelated to the gymnastics sex abuse scandal.

More than 150 women and girls have accused Nassar of assaulting them during their time at Michigan State, with USA Gymnastics or with Michigan’s Twistars Gymnastics Club. Nassar pleaded guilty to molesting at least two teenagers at Twistars, according to The Detroit News. Many victims claimed Nassar inserted ungloved fingers into their vaginas and told them he was simply giving them medical treatment.

Nassar pleaded guilty in November to several counts of first-degree criminal sexual conduct.

Some of Gymnastics Biggest Stars Have Accused Nassar of Abuse

Last October, McKayla Maroney, 21, wrote in a Twitter post that Nassar began molesting her when she was 13 years old. She recalled an incident when she was 15 in which she claimed Nassar drugged her during a flight to Tokyo and abused her. Shortly after, Maroney’s fellow gymnast Aly Raisman came forward, accusing Nassar of abusing her several times beginning when she was 15.

“I didn’t think I was being molested. I didn’t know,” Raisman said. “He was a doctor. I never would have thought that a doctor would misuse his power so much.”

Gabby Douglas, who competed alongside Raisman in last year’s Olympics, said in November that she too was abused by the doctor. Most recently, Simone Biles said her friends gave her the courage to speak out about her “horrible experience” with the doctor.

USA Gymnastics Cut Ties with the Famous Karolyi Ranch

Last week, USA Gymnastics announced that they had cut ties with the Karolyi Ranch — the legendary 40-acre camp used to train gymnasts for years — where several athletes have said they were sexually abused by Nassar. The Huntsville, Texas, ranch, run by famed coaches Marta and Bela Karolyi, has long been credited for producing some of the world’s greatest gymnasts. However, the once-beloved ranch has come under scrutiny in recent years, as several former gymnasts have said the couple did nothing to protect them although they allegedly knew Nassar was abusing gymnasts at the camp.

At the camp, gymnasts slept in cedar log cabins with air conditioning, bathrooms, and showers inside. It was there that former gymnast Jeanette Antolin said that Nassar abused her. She claims the Karolyis knew Nassar was alone in the cabins with the girls.

“They had to know. I mean, there — there was no one else sent with him,” she told told 60 Minutes. “And that’s the thing, too, to think, like– what– they– in– in the bed? Why would you – like, the treatment was in the bed, in my bed that I slept on at the ranch.”

An attorney for the Karolyis have denied the allegations.

USA Gymnastics and the U.S. Olympic Committee Have Come Under Fire

As Nassar has sparked outrage as a result of his behavior, many have criticized the organizations for turning a blind eye to the abuse. The Indianapolis Star reported that USA Gymnastics kept several sexual misconduct allegations under wraps, and did not usually report accusations to police. In her victim impact statement, Raisman chided the organization for apparently protecting Nassar and intimidating victims who came forward.

“USA Gymnastics, where is the honesty? Where is the transparency? Why must the manipulation continue? Neither USA Gymnastics nor the USOC have reached out to express sympathy or even offer support,” she said.

“It is like being abused all over again. I have represented the United States of America in two Olympics and have done so successfully. Both USA Gymnastics and the United States Olympic Committee have been very quick to capitalize and celebrate my success, but did they reach out when I came forward? No.”

In several statements, USAG said that they first learned of Nassar’s abuse in the summer of 2015 and quickly fired him. Organization officials said in a later statement: “USA Gymnastics is appalled that anyone would exploit a young athlete or child in the manner alleged. When USA Gymnastics first learned of athlete concerns regarding Dr. Nassar in the summer of 2015, the organization acted without hesitation.

RELATED VIDEO: Gabby Douglas Says She Was Abused by Former Team Doctor Larry Nassar

The officials have praised several victims for coming forward about their experiences with Nassar.

In a statement on Wednesday, USOC officials issued an apology to Nassar’s victims:

“The purpose of this message is to tell all of Nassar’s victims and survivors, directly, how incredibly sorry we are,” CEO Scott Blackmun said in the statement. “We have said it in other contexts, but we have not been direct enough with you. We are sorry for the pain caused by this terrible man, and sorry that you weren’t afforded a safe opportunity to pursue your sports dreams.”

USOC officials later said in a statement to PEOPLE: “We have proactively arranged for multiple independent reviews of our safe sport policies and practices since 2010. We are open to any further process or review that could lead to a safer environment for athletes who participate in Olympic and Paralympic sports.”

USA Gymnastics Saw a Major Change In Leadership Throughout the Scandal

In March 2017, USA Gymnastics president Steve Penny resigned after the USOC called for him to step down amid the sex abuse scandal. He was replaced by Kerry Perry.

USA Gymnastics Board of Directors’ Chairman Paul Parilla, Vice Chairman Jay Binder and Treasurer Bitsy Kelley all tendered their resignations effective Sunday, according to Perry.

“We support their decisions to resign at this time,” Perry also said, per a statement posted on the group’s website. “We believe this step will allow us to more effectively move forward in implementing change within our organization.”

Although the statement did not mention Nassar by name, it said “USA Gymnastics has and will continue to take specific and concrete steps to promote athlete safety, health and well-being and prevent future abuse by adopting and vigorously enforcing the USA Gymnastics Safe Sport Policy.”

USA Gymnastics also suspended former U.S. women’s national team coach John Geddert, the owner of the Twistars gymnastics club near Lansing, multiple outlets reported.