(TNS) — A cyber criminal gang that breached the Washington, D.C., Metropolitan Police Department’s computer network in a ransomware attack published detailed information last week about nearly two dozen officers, including Social Security numbers and psychological assessments.

The group, Babuk, already had posted on the dark web lengthy dossiers of several officers. It claimed it stole more than 250 gigabytes of data late last month and is threatening to release more information as well as share files containing the names of confidential informants with criminal gangs if officials don’t pay a ransom.

The most recently posted documents contain sensitive information about 22 officers, such as fingerprints, dates of birth, polygraph test results and residential, financial and marriage history, according to NBC News. The hackers claim that they demanded $4 million in ransom and the department countered with $100,000, which they deemed unacceptable.

“This was the most serious incident involving a police department that we’ve seen to date. It doesn’t get much worse,” said Brett Callow, a threat analyst for cybersecurity company Emsisoft. “The release of that information could put officers and civilians at risk.”

A separate ransomware attack forced the recent shutdown of the Colonial Pipeline, leading to panic buying and gas shortages on the East Coast. Cyber criminals also have launched ransomware attacks on school districts, health care systems, courts and local government offices.

But when the hackers have struck police departments, cybersecurity experts say, they pose a particularly serious threat to public safety.

Ransomware attacks have taken down 911 systems, prevented officers from checking suspects’ criminal histories during traffic stops and blocked access to investigative files or video, impeding investigations. In some cases, prosecutors have had to drop criminal cases.

“We equate it to kidnapping,” said Jonathan Thompson, executive director of the National Sheriffs’ Association. “In this case, the victim is the data, but most importantly, it’s the community. Law enforcement has to…