WASHINGTON (AP) — Edward Snowden says he repeatedly raised constitutional concerns about National Security Agency surveillance internally, but an NSA search turned up a single email in which Snowden gently asks for “clarification” on a technical legal question about training materials, agency officials said Thursday.

Snowden, a former NSA systems administrator whose leaks have exposed some of the agency’s most sensitive spying operations, called himself a patriot in an interview this week with NBC News’ Brian Williams. He said he felt he had no choice but to expose what he considered illegal NSA surveillance by leaking secret details to journalists.