After President Donald Trump fired Attorney General Jeff Sessions on Wednesday, Sen. Bernie Sanders said that any further move by the president to impede or interfere with the ongoing investigation by Special Counsel Robert Mueller would be considered an “obstruction of justice and impeachable offense.”

“Trump must allow Special Counsel Robert Mueller’s investigation to continue unimpeded,” the tweet reads. “Any attempt by the president or the Justice Department to interfere with Mueller’s probe would be an obstruction of justice and impeachable offense.”