On Friday, December 1, former National Security Adviser Michael Flynn pleaded guilty to lying to the FBI about contacts he had with Russia’s Ambassador to the U.S. Sergey Kislyak. Flynn is the fourth person associated with the Trump campaign to be charged and the first person to serve in Trump’s White House to be charged and plead guilty. Sources say that Flynn is now in full cooperation with Special Counsel Robert Mueller and his team, who continue to dive further and further into Trump’s associates and potential contacts and collusion with Russians close to the Russian government.

During the 2016 campaign, Flynn was a personal friend and a passionate supporter of Donald Trump, and often tagged along with Trump on the campaign trail. After the election, Trump named Flynn as his National Security Advisor. On January 24, just four days into his service as National Security Advisor, Flynn allegedly lied to FBI investigators regarding his contacts with Russians, and then subsequently lied to the Vice President as well, which ultimately led to Flynn’s resignation on February 13. Flynn’s tenure lasted just 24 days, which is the shortest ever for a President’s National Security Advisor since the position was creating 63 years prior under President Harry Truman.

In the plea, Flynn outlines two senior Trump officials who directed him to have contacts with officials from foreign governments, including Russia. Several news outlets report from sources that the two senior officials are Jared Kushner, the President’s son-in-law is a top advisor to the president, and K.T. McFarland, the current Deputy National Security Advisor and current nominee to be the next United States Ambassador to Singapore. While the Flynn plea deal does not directly implicate Trump, sources say Mueller is beginning to look into Trump’s financial records, which could signal trouble for Trump.