The day before Larry Nassar's sentencing, McKayla Maroney and her mother release victim impact statements to the judge. (1:20)

Editor's note: This story contains details that may be disturbing for some readers.

GRAND RAPIDS, Michigan -- McKayla Maroney had planned to be in a federal courtroom Thursday to deliver a victim-impact statement in open court in the case of Larry Nassar, the disgraced former doctor for Team USA who, Maroney says, sexually abused her for six years.

Instead, Maroney's testimony will come in the form of letters written by her, which have been made public, and her mother, which were obtained by Outside the Lines, to the federal judge presiding over the case. The letters provide a chilling account of the psychological toll Nassar's alleged abuse took on the former member of the "Fierce Five," the gold-medal-winning women's gymnastics team from the 2012 London Olympics.

The judge ruled last week that victim-impact statements could not be read out loud in court. Instead, she will read them privately.

Maroney was arguably the most recognizable face of that Olympic team, rising to national prominence through a series of national television appearances and a trip to the White House.

"This experience has shattered McKayla," Erin Maroney wrote in a letter describing her daughter's ordeal. "She has transformed from a bubbly, positive, loving, world class athlete into a young adult who was deeply depressed, at times suicidal. At times, I was unsure whether I would open her bedroom door and find her dead."

Gold-medal gymnast McKayla Maroney, in a letter to the federal judge presiding over the Larry Nassar case, said the former USA Gymnastics doctor "deserves to spend the rest of his life in prison." Mark J. Rebilas/USA TODAY Sports

McKayla Maroney says Nassar began abusing her under the guise of medical care at the famed Karolyi Ranch -- the USA Gymnastics' national team training center run by former Team USA coaches Bela and Marta Karolyi.

"It started when I was 13 years old, at one of my first national team training camps, in Texas, and it didn't end until I left the sport," Maroney wrote in her letter to the court. "Because the national team training camps did not allow parents to be present, my mom and dad were unable to observe what Nassar was doing."

Erin Maroney wrote that she and her husband "were not allowed to stay with McKayla" during travel abroad and "sometimes we were not even in the same hotel."

"We were never allowed to the U.S. Olympic Training Center at the Karolyi Ranch nor any other training facility," Erin Maroney wrote. "My husband once questioned the propriety of the isolation of the girls during international travel. He was assured by Steve Penny that the girls were safe at all times. 'More safe than the President of the USA,' he said to him. We now know that this was a lie."

Penny resigned in March amid mounting criticism of the way he handled the sexual-abuse problem.

One of the more disturbing incidents, described in the letters by both women, occurred when Maroney competed in the 2011 world championships in Tokyo.

"I ... learned a few weeks ago from my daughter that at the world championships in Tokyo, [Nassar] drugged her, made her lay nude on a treatment table, straddled her and digitally penetrated her while rubbing his erect penis against her," Erin Maroney wrote. "She was only 15 years old. She said to me, 'Mom I thought I was going to die.'

"I cannot tell you the anguish her Dad and I feel and the responsibility we feel for not being aware of this or being able to stop it."

McKayla Maroney described the incident as well in her letter, saying Nassar "had given me a sleeping pill for the flight, and the next thing I know, I was all alone with him in his hotel room getting treatment."

USA Gymnastics policies forbid adults from being alone with minors, but Maroney and several other national team gymnasts have described multiple incidents to ESPN where Nassar abused them in their dorm rooms at the Karolyi Ranch, in hotels during international competitions and in athletes villages at the Olympics.

"It happened in London before my team and I won the gold medal, and it happened before I won my silver medal," Maroney wrote, describing the times she says Nassar sexually assaulted her during the 2012 London Olympics.

McKayla and Erin Maroney reserved harsh criticism for the institutions they say enabled Nassar: USA Gymnastics, the U.S. Olympic Committee and Nassar's full-time employer, Michigan State.

"Our daughter was totally failed by USA Gymnastics, by Michigan State University and by the U.S. Olympic Committee. No one from the USOC has ever reached out to me or my husband or my daughter to inquire about her well being. Not once. No one has apologized," Erin Maroney wrote. "After McKayla spoke with an investigator with USA Gymnastics in July 2015, USA Gymnastics and the USOC kept the knowledge of [Nassar's] status as a child molester secret from Michigan State University after 2015 and even said nothing when he ran for school board in his local school district!"

At Michigan State, concerns about Nassar's behavior during medical appointments can be traced back to the late 1990s. Four women have told Outside the Lines that they went to coaches or athletic trainers in the late '90s, explaining that they had been digitally penetrated during treatment sessions. The women all say their complaints were dismissed.

"A simple fact is this. If Michigan State University, USA Gymnastics and the U.S. Olympic Committee had paid attention to any of the red flags in Larry Nassar's behavior, I never would have met him, I never would have been 'treated' by him and I never would have been abused by him," McKayla Maroney wrote.

Michigan State has consistently declined to comment on individual allegations. But after Nassar pleaded guilty in November to 10 counts of criminal sexual conduct, including multiple counts involving the abuse of patients 13 years old or younger, the school issued a statement.

"Michigan State University continues to be shocked and appalled by Larry Nassar's now-admitted criminal conduct," the university's statement said. "Any suggestion that the university covered up this conduct is simply false."

Nassar's sentencing Thursday in a federal child pornography case in western Michigan could result in a life sentence. Under the terms of a plea agreement he signed in July, Nassar could receive a minimum sentence of 27 years. But in recent court filings, federal prosecutors have asked the court to impose a 60-year sentence.

Nassar admits that, between 2003 and 2016, he downloaded thousands of images and videos of child pornography.

An FBI special agent testified at Nassar's arraignment last December in the federal case, saying that hard drives, recovered in Nassar's trash can, contained approximately 37,000 images and videos of child pornography, with images of girls as young as 6 or 7 being sexually violated.

"How many more images were on his computer at Michigan State University that he erased? Were McKayla's images on there? Were his other victims? Did he trade those images with other pedophiles? Are those images on the dark web today? These are questions that keep my husband and I up at night," Erin Maroney wrote. "I know this also haunts my daughter. Will she wake up one day to find an image of her 13-year-old self being assaulted on the internet? This is what our family must live with and it will never go away."

While Maroney is arguably the highest-profile gymnast to publicly claim abuse by Nassar, she is by no means alone.

Former Fierce Five teammates Aly Raisman, who won six medals while serving as the captain of the U.S. women's team in 2012 and 2016, and Gabby Douglas, the 2012 Olympic all-around champion, have also said they were abused.

Jamie Dantzscher, a bronze medalist on the 2000 U.S. Olympic team, was part of the initial wave of lawsuits filed against Nassar in 2016.

Since then, more than 140 women have filed lawsuits against Nassar, USA Gymnastics, Michigan State and high-ranking officials from both institutions.

"He abused my trust, abused my body and left scars on my psyche that may never heal," McKayla Maroney told the court in her letter. "Larry Nassar deserves to spend the rest of his life in prison."