When a ship is going down, the rats begin to flee. The same is true when it comes to the downfall of a powerful public official.

On Sept. 26, federal prosecutors unsealed an indictment against Eric Adams, charging the New York mayor with fraud, bribery, conspiracy and soliciting illegal campaign donations from foreign donors. The detailed 57-page indictment alleges that as a result of illegally obtained campaign funds, Adams fraudulently received more than $10 million in public matching funds. The indictment further accuses Adams of accepting bribes in the form of luxury international travel accommodations valued at more than $100,000 from foreign nationals in exchange for favors.

Adams has denied the allegations, and pleaded not guilty in federal court. However, the indictment appears to reflect a strong case because it provides great detail about the evidence in support of the allegations, including direct and damming quotations from text and email messages.

During a news conference announcing the charges, Manhattan U.S. Attorney Damian Williams said the investigation remains ongoing and that his office would “hold more people accountable.” He encouraged those with information about criminal conduct by the mayor to come forward “before it’s too late.”

The charges brought to mind a case I supervised when I served as U.S. attorney for the Eastern District of Michigan. Former Detroit Mayor Kwame Kilpatrick was a talented and popular mayor first elected in 2002 and reelected in 2006. He would later be convicted on charges of racketeering conspiracy for using his office to enrich himself and associates through fraud, bribery, extortion and tax evasion.

But the evidence didn’t come to prosecutors immediately. Witnesses and victims of shakedowns were reluctant to come forward against a powerful public official who had the authority to award and deny lucrative public works contracts. Others had their own culpability for going along with pay-to-play schemes, providing kickbacks in exchange for receiving multi-million dollar contracts to provide construction and other services to the city.

It took two events to get witnesses talking. First was a 2008 perjury conviction in state court, which resulted in Kilpatrick’s resignation. Kilpatrick admitted to falsely denying an extramarital affair from the witness stand in a wrongful discharge case brought by a former bodyguard. Once the mayor was out of office, he lacked the power he had previously wielded. Suddenly, people were more willing to cooperate with prosecutors.

The second event was a federal indictment for fraud and income tax evasion. Once witnesses realized that a long-rumored federal investigation was coming to fruition, they calculated that it was better to be a witness than a defendant. Their cooperation led to additional evidence that resulted in a superseding indictment with more serious corruption charges against Kilpatrick and others.

All told, more than 30 defendants who worked in the Kilpatrick administration or did business with the city were convicted of federal crimes. Those who cooperated received leniency in their sentencing. Kilpatrick was sentenced to 28 years in prison. President Donald Trump commuted his sentence after seven years.

The language of the Adams case suggests that more charges and more defendants may await. New charges may include obstruction of justice (based on text messages quoted in the indictment that suggest a coverup) and income tax evasion (unless Adams reported his lavish travel gifts as income). Additional defendants could include the staffers who the indictment alleges assisted in the commission of crimes.

New charges might even include additional schemes. Questions have been raised by the recent resignations of the mayor’s chief counsel and the city’s police commissioner and the announced departures of the public schools chancellor and health commissioner. Searches conducted at the homes of two people who raised money for Adams also suggest that more individuals or schemes may be subjects of investigation.

The language of the indictment, alleging specific incidents and conversations, makes it likely that prosecutors have already secured cooperation from some participants. Williams’s request makes it clear that he is seeking others. By inviting more people to come forward, Williams may be speaking directly to those who, until today, were either too arrogant to believe they would be charged or too fearful of retaliation to admit any knowledge of criminal misconduct to law enforcement.

One more step could provide an additional incentive to come forward. While Adams has stated that he will not resign his office, under New York law, the state’s governor, Kathy Hochul, also has the power to remove Adams as mayor. Without the power of office, Adams becomes just another defendant.

Once people can see what appears to be strong evidence of serious charges, they may calculate that the time has come to jump ship and save themselves.

Barbara McQuade is a professor at the University of Michigan Law school.