Former FBI Director James Comey seemingly responded Sunday on Twitter to the release of key findings from Special Counsel Robert Mueller's Russia investigation -- saying he had questions. "So many questions," Comey tweeted, alongside a photo of himself in a forest, looking upwards while surrounded by tall trees. Mueller was appointed special counsel of the Russia probe shortly after President Trump had fired Comey in May 2017. Hours before Comey's tweet, Attorney General William Barr released a four-page letter detailing what he called the "principal conclusions" of Mueller's investigation into possible collusion between President Trump's 2016 campaign and Russia.