CNN  — 

On Thursday we learned that federal prosecutors in Pennsylvania have taken a step long-sought by survivors of clergy sexual abuse: They launched a federal investigation into the Catholic Church.

All eight of Pennsylvania’s dioceses have received subpoenas and have told CNN they will cooperate with the probe. Separately, the diocese of Buffalo, New York, also received a subpoena regarding clergy sexual abuse in late May.

While the scope of the federal investigation is still unclear, groups like the Survivors Network of those Abused by Priests, which first asked the Department of Justice to launch a probe in 2003, called Thursday’s news unprecedented.

There has never been a federal investigation of this size into the abuse of children by priests and the cover-up of those crimes by Catholic leaders, according to former law enforcement officials and experts on clergy misconduct in the United States.

“It is essential to involve federal resources to fully and finally get to the bottom of a scandal that has been going on for decades, and I say that both as a former federal prosecutor and a Catholic,” said David Hickton, who was US Attorney for the Western District of Pennsylvania from 2010-2017.

“There is no excuse anymore for the church policing itself.”

But there are still a lot of questions about the federal probe. The Justice Department has declined to comment, as has the Eastern District of Pennsylvania, which issued the subpoenas, according to the Associated Press.

Here’s what we do and don’t know thus far.

What are prosecutors looking for?

The subpoenas were issued by US Attorney William McSwain, according to the AP, and ask for years of internal church records, including any evidence that Catholic clergy may have transported children across state lines for illicit purposes or shared child pornography online or electronically.

Prosecutors also appear to be looking for evidence that Catholic leaders covered up priests’ crimes by shuffling them to new parishes and instructing victims and their families not to tell police, according to the Washington Post.

That evidence could be used to bring a racketeering case against Catholic leaders, said Hickton.

“Human trafficking, child pornography, the Mann Act – any of these could be the underlying crimes for RICO,” he said, referring to the Racketeer Influenced and Corrupt Organizations Act, a law originally designed to target the Mafia.

Who are prosecutors targeting?

The federal investigation originated in Pennsylvania, rather than Justice Department headquarters in Washington, according to the AP.

While we don’t yet know the full scope of this probe, we know that all eight of Pennsylvania’s eight Catholic dioceses have already received subpoenas: Allentown, Erie, Greensburg, Harrisburg, Pittsburgh, Scranton and the Archdiocese of Philadelphia. The state’s eighth diocese, Altoona-Johnstown, was the last to acknowledge the subpoenas, on October 23.

In 2017, Altoona-Johnstown reached a “memo of understanding” with federal prosecutors in Western Pennsylvania. That memo requires diocesan officials to report all accusations of child sexual abuse by clergy to law enforcement within 12 hours of receipt and maintain an independent advisory board.

Separately, the Justice Department subpoenaed the Buffalo diocese in late May, a source with knowledge of the federal subpoena told CNN.

The source said the subpoena sought diocesan documentation regarding pornography, taking victims across state lines, and inappropriate use of cell phones and social media.

A spokeswoman for the Diocese of Buffalo said it received a request from the US attorney’s office several months ago to review documents.

“A subpoena was provided and after some discussion, an agreement was reached to produce documents,” communications director Kathy Spangler said. “We have heard nothing since early June. As far as we know, our response has nothing to do with the current Pennsylvania investigation that has just begun.”

Why now?

In August, a statewide grand jury released a report detailing extensive sexual abuse and cover ups in six Catholic dioceses in Pennsylvania. Since 1947, the report said, 301 priests had abused more than 1,000 victims.

Because of Pennsylvania’s statute of limitations, only two priests were charged with crimes related to the two-year-long probe. Both pleaded guilty.

As part of their report, the 23 grand jurors issued a series of recommendations, including eliminating the statute of limitations for victims to file criminal complaints and outlawing non-disclosure agreements, which they said were used to silence victims.

News of the federal investigation into Pennsylvania dioceses became public just one day after state lawmakers failed to approve any of those measures.

“The action of the Pennsylvania State Senate is shameful,” said Hickton. “It is transparent that they are in the pocket of the Catholic Church.”

Pennsylvania’s Catholic bishops did support an independent compensation program for clergy abuse victims.

“We recognize our responsibility to provide an opportunity for sexual abuse survivors whose cases are time-barred from pursuing civil claims to share their experiences, identify their abusers, and receive compensation to assist their healing and recovery,” the bishops said.

What about the other investigations into the Catholic Church?

Since the Pennsylvania grand jury report, a number of Catholic dioceses have said they have launched internal investigations.

But that may not be enough for lay Catholics, or for law enforcement officials. In September, the New York attorney general issued civil subpoenas for all eight Catholic dioceses in the state as part of a civil investigation into how the dioceses and other parts of the church reviewed and potentially covered up allegations of the sexual abuse of minors, according to a source close to the investigation.

New Jersey’s attorney general has also said his office would form a task force to investigate allegations of sexual abuse by clergy and any attempted cover-ups.

Attorneys general in Missouri and New Mexico say they are also investigating church files for evidence of abuse and cover ups.

Hickton, the former federal prosecutor, said the Justice Department has preferred to let state officials take the lead in investigating Catholic dioceses.

But like many other Catholics, Hickton said the full scope of the abuse scandal can only be uncovered by a national probe that would look at all 196 Catholic diocese in the United States, along the lines of Australia’s Royal Commission report.

Published in 2017 after a five-year investigation, that report found 4,444 alleged cases of abuse between 1950 and 2009.

“We need something like that here in the United States,” said Terry McKiernan, who runs the watchdog website “That’s the only way we’re ever going to know the full truth.”

CNN’s Rosa Flores contributed to this report.