The department reported that it arrested Jackson A. Cosko for allegedly posting “private, identifying information (doxing) about one or more United States senators to the Internet.” Cosko has been working as an intern in the office of Democratic Rep. Sheila Jackson Lee of Texas and has been fired, according to her chief of staff Glenn Rushing.

“We’re just cooperating with law enforcement right now,” Rushing said in an interview.

Cosko graduated from George Washington University in 2014 and previously worked for Democratic Sens. Maggie Hassan of New Hampshire and California’s Barbara Boxer, who has since retired. Cosko most recently worked for Hassan as a “legislative correspondent/systems administrator,” according to Legistorm.