Edward Snowden leaked as many as 200,000 classified U.S. documents to the media this year, according to NSA chief Gen. Keith Alexander.

Alexander made the comments after a speech in Baltimore last month, Reuters reported Thursday. The news service obtained a copy of the October event’s transcript from the National Security Agency.

“I wish there was a way to prevent it. Snowden has shared somewhere between 50 [thousand] and 200,000 documents with reporters. These will continue to come out,” Alexander said, according to the report.

The leaked documents are “being put out in a way that does the maximum damage to NSA and our nation,” said Alexander, who plans to leave the agency in March or April 2014.

Government officials familiar with the Snowden case have previously said the number of documents the former contractor gained access to was in the hundreds of thousands.