Journalist and activist Barrett Brown has been released from federal prison, after he was arrested Thursday—only one day before he was slated to be interviewed for an upcoming PBS documentary. He was imprisoned for unknown reasons. His arrest came after he served four years behind bars on charges related to the hacking of the private intelligence firm Stratfor, which exposed how the firm spied on activists on behalf of corporations. Last year, Brown won the National Magazine Award for prison columns, for a series of columns he wrote for The Intercept.