The documents were released through an official FBI records Twitter account.
In the statement, Sessions said President Donald Trump "has exercised his lawful authority to remove James B. Comey, Jr., as the Director of the Federal Bureau of Investigation." He also named Deputy Director Andrew McCabe as acting director.
The second document is a letter from McCabe to FBI staff, sent on May 12 after what he described as a "tough week" of adjusting to Comey's absence.
"We all miss him. And I know that he misses us," McCabe wrote.
He called on the staff to stay focused on the mission of the agency, despite the recent upheaval.
"So please — hang in there. As men and women of the FBI, we are at our best when times are tough. Please stay focused on the mission, keep doing great work, be good to each other and we will get through this together," he said.