A former National Security Agency (NSA) chief giving off-the-record interviews on a high-speed train has had his remarks reported live on Twitter.
General Michael Hayden was talking off-the-record to journalists by phone when he was overheard by another passenger, a former political activist.
Tom Matzzie said he waited half an hour before live-tweeting comments about US renditions and a "famous BlackBerry".
The comments went viral on news websites and late-night television.
Gen Hayden, who was alerted to the Twitter feed within about 15 minutes, then offered an interview to Mr Matzzie, who is now head of a company called Ethical Electric.
"I just had a very nice conversation with Michael Hayden. He was a gentleman and we disagree," Mr Matzzie later tweeted.
The two men were on a high-speed Acela train travelling from Washington, DC to New York late on Thursday afternoon.
Mr Matzzie began tweeting details of the conversations from what he said was a distance of 8ft (about 2.4m) away.
"On Acela listening to former NSA spy boss Michael Hayden give 'off record' interviews. I feel like I'm in the NSA. Except I'm in public," Mr Matzzie's Twitter feed read.
The National Security Agency has come under intense criticism after revelations by ex-CIA contractor Edward Snowden that US intelligence conducted extensive web and phone surveillance on targets at home and abroad.
Mr Snowden now faces espionage charges in the US and has been granted temporary asylum in Russia.
Gen Hayden has defended his former agency's operations in the past and Mr Matzzie wrote that Thursday's interviews were also focused on NSA surveillance of foreign allies.
As the former head of MoveOn.org Political Action, Mr Matzzie once campaigned against the US-led war in Iraq.
He made clear his own feelings about the former NSA and CIA chief with a tweet reading, "There is a faint smell of sulfur on the train."
He said Gen Hayden asked journalists to refer to him as a "former senior administration official" for comments described as "disparaging" to President Barack Obama's administration.
Gen Hayden later gave a statement to the Reuters news agency saying he "didn't criticise" the president.
"I actually said these are very difficult issues. I said I had political guidance, too, that limited the things that I did when I was director of NSA. Now that political guidance is going to be more robust. It wasn't a criticism," Gen Hayden said.