At least 1,000 children were molested by hundreds of Roman Catholic priests in six Pennsylvania dioceses, as senior church officials took steps to cover it up, according to a landmark grand jury report released Tuesday.

The grand jury report, which states in excess of 300 clergy committed abuse over a period of decades from the mid-1950s, the “real number” of abused children could be “in the thousands,” since numerous records were either lost or victims were afraid to come forward. Pennsylvania Attorney General Josh Shapiro announced the two-year investigation found a systematic cover-up by senior church officials in both the Keystone State and the Vatican.

“The cover-up was sophisticated. And all the while, shockingly, church leadership kept records of the abuse and the cover-up,” said Shapiro at a press conference in Harrisburg. “These documents, from the dioceses’ own ‘Secret Archives,’ formed the backbone of this investigation.”

One Pennsylvania priest sexually abused five sisters from the same family over a period of a decade. The youngest of the girls was just 18-months-old, according to the report. In another case, a priest raped and impregnated a girl, later arranging for the fetus to be aborted.

“The grand jury detailed that the coverups by the church served a key purpose – the longer they covered up abuses, the less chance that law enforcement could prosecute predator priests because the statute of limitations would run out,” said Shapiro.

Among other explosive findings, the report faulted Cardinal Donald Wuerl, a former longtime bishop of Pittsburgh who now leads the Washington archdiocese, for what it said was his role in the concealment of clergy sexual abuse. Wuerl, one of the highest-profile cardinals in the United States, released a statement Tuesday that said he had “acted with diligence, with concern for the victims and to prevent future acts of abuse.”

Cardinal Donald Wuerl of DC, who was bishop of Pittsburgh from 1988-2006 and whose actions as bishop are chronicled in the report, also released a statement, calling sexual abuse of children "a terrible tragedy" and defending his own record. pic.twitter.com/0OoywP1NUW — Michael J. O'Loughlin (@MikeOLoughlin) August 14, 2018

The grand jury scrutinized abuse allegations in dioceses that minister to more than half the state’s 3.2 million Catholics. Its report echoed the findings of many earlier church investigations around the country in its description of widespread sexual abuse by clergy and church officials’ concealment of it. Most of the victims were boys, but girls were abused, too, the report said. The abuse ranged from groping and masturbation to anal, oral, and vaginal rape.

“Church officials routinely and purposefully described the abuse as horseplay and wrestling and inappropriate conduct. It was none of those things. It was child sexual abuse, including rape,” the Pennsylvania Attorney General said.

The panel concluded that a succession of Catholic bishops and other diocesan leaders tried to shield the church from bad publicity and financial liability by covering up abuse, failing to report accused clergy to police and discouraging victims from going to law enforcement.

The document comes at a time of renewed scrutiny and fresh scandal at the highest levels of the U.S. Catholic Church. Pope Francis stripped 88-year-old Cardinal Theodore McCarrick of his title and ordered him to a lifetime of prayer and penance amid allegations that McCarrick had for years sexually abused boys and had sexual misconduct with adult seminarians.

Wuerl has come under harsh criticism over his response to the McCarrick scandal, with some commentators questioning his claims of surprise and ignorance over allegations that McCarrick molested and harassed young seminarians. Wuerl replaced McCarrick as Washington’s archbishop after McCarrick retired in 2006.

The Pennsylvania grand jury, convened by the state attorney general’s office in 2016, heard from dozens of witnesses and reviewed more than a half-million pages of internal documents from the Allentown, Erie, Greensburg, Harrisburg, Pittsburgh, and Scranton dioceses.

A group of current and former clergy named in the report went to court to prevent its release, arguing it violated their constitutional rights to reputation and due process of law. The state Supreme Court said the public had a right to see it, but ruled the names of priests and others who objected to the findings would be blacked out pending a September hearing on their claims. The identities of those clergy members remain under court seal.

A couple of dioceses decided to strip the accused of their anonymity ahead of the report and released the names of clergy members who were accused of sexual misconduct. On Friday, the bishop of Pittsburgh’s diocese said a few priests named in the report are still in ministry because the diocese determined allegations against them were unsubstantiated.

However, the grand jury’s work won’t result in justice for the vast majority of those who say they were molested by priests as children. While the probe yielded charges against two clergymen — including a priest who has since pleaded guilty, and another who allegedly forced his accuser to say confession after each sex assault — the other priests identified as perpetrators are either dead or will avoid arrest because their alleged crimes are too old to prosecute under state law.

“We are sick over all the crimes that will go unpunished and uncompensated,” the grand jury said. “We are going to name their names, and describe what they did — both the sex offenders and those who concealed them.”

“[W]e are going to make our recommendations for how the laws should change so that maybe no one will have to conduct another inquiry like this one,” the grand jury added.

The Associated Press contributed to this report.