A ransomware attack that started with an e-mail to a police employee has cost the city of Riviera Beach, FL, 65 bitcoin worth approximately $592,000.

Riviera Beach, a small city of about 35,000 people just north of West Palm Beach, is the latest government to be crippled by ransomware attacks that have successfully extorted municipalities and forced them to dig into public coffers to restore their networks. A similar breach recently cost Baltimore $18 million to repair damages.

Most ransomware attacks tend to involve nominal amounts of money. The large ransom extorted from Riviera Beach has some experts worried that hackers have become emboldened by their increasingly sophisticated ability to target government agencies, the New York Times reports.

The Riviera Beach attack began on May 29 after a police department employee opened an infected email attachment, The Palm Beach Post reported. Down went all of the city’s online systems, including email and some phones, as well as water utility pump stations. Utility payments could not be accepted other than in person or by snail mail — and even then, only by check or cash.