From UPMatters:

Christodoulos Santafianos has agreed to plead guilty to theft or conversion of a government record. He faces up to a year in prison and up to a $100,000 fine. As part of the plea agreement, Santafianos must also resign from ATF.

Santafianos starting working for ATF in 2015, court records say. In 2019, he started releasing records to someone connected with gun rights advocacy groups; he sent hundreds of records and communications to the guns rights activist over the next few years, court records say. The advocacy groups often made information in the records public, sometimes the day after Santafianos sent them over, court records say.