Edward Snowden, a 29-year-old system administrator and former undercover CIA employee, unmasked himself Sunday as the principal source of recent Washington Post and Guardian disclosures about top-secret NSA programs, denouncing what he described as systematic surveillance of innocent citizens and saying in an interview, “it’s important to send a message to government that people will not be intimidated.”

Director of National Intelligence James R. Clapper Jr. said Saturday that the NSA had initiated a Justice Department investigation into who leaked the information.