Washington (CNN)The country's No. 2 intelligence official, Sue Gordon, knew it was likely she would have to eventually step down from her post, but the timing of that decision became more urgent on Thursday after her boss -- outgoing spy chief Dan Coats -- interrupted a meeting she was holding on election security and asked his deputy to submit her letter of resignation, sources familiar with the events told CNN.

While details of the conversation between Gordon, an intelligence veteran of more than 30 years, and Coats remain unclear, sources say that the situation clearly abruptly changed after the meeting was interrupted.