The lawyers for Michael T. Flynn, President Donald Trump‘s former National Security Adviser, have notified Trump’s legal team that they will no longer be communication between the two parties about the investigation.

The investigation lead by special counsel Robert S. Mueller III is investigating possible collusion between the Trump campaign and the Russian government to sabotage presidential candidate, Hillary Clinton’s 2016 campaign. Mueller has been targeting Flynn for some time now.

Flynn’s legal team had been cooperating with the President’s lawyers and were sharing information. It is normal for defense lawyers to communicate information between one another during investigations. Both parties must cut communication ties once the sharing of information becomes a conflict of interest.

The notification from Flynn’s legal team to President Trump’s team is rather unsettling for them. The news could signify that Flynn has begun negotiations with Mueller. If it is true, a deal with Flynn, would be a break through in the case for special counsel Mueller. Flynn had been an important supporter of Trump and his campaign. Cooperation from Flynn could give Mueller information on the early days of Trump’s administration and his presidential campaign. The former National Security Advisor was an advocate for Trump’s “America first” platform and also has had known ties with Russia since 2015.

Trump named Flynn his National Security Advisor, despite warnings from many including President Obama. It was just 24 days into Flynn’s role as National Security Advisor, when news broke about his communications with Russian ambassador, Sergey Kislyak. Additional reports suggested that Flynn had also misled the Vice President Mike Pence on these communications. On February 13, 2017, Flynn resigned from his position as National Security Advisor. The special counsel’s office is known to be investing Flynn’s links to the Turkish government.