The false claim originated from fake Twitter account, but was shared in a post (archived here) published by the People of Bernie Sanders Facebook group on November 16, 2019 under the title "Whoopsie. Robert Mueller tweets back...". It opened:
Six Former Trump advisers, 26 Russian nationals, three Russian companies, one California man, and one London-based lawyer. Seven of these people (includin five of the six former Trump advisers) have pleaded guilty.All of these charges stem from our investigation.
This is what social media users saw:
The purported Mueller tweet was a reply to this real Trump tweet:
"Not a single American citizen has been charged with anything related to Russian Collusion, not one person." @TuckerCarlson It was all an illegal Witch Hunt!
"Not a single American citizen has been charged with anything related to Russian Collusion, not one person." @TuckerCarlson It was all an illegal Witch Hunt!
-- Donald J. Trump (@realDonaldTrump) October 26, 2019
After the fake tweet gained attention on social media, the account was suspended by Twitter.
Robert Mueller has been famously reluctant to publicly comment on the results of his investigation. Even when called to testify before congress, he was tight lipped, sticking close to the words published already in his report.