White House Press Secretary Sean Spicer told reporters at the White House that President Donald Trump asked his national security adviser Gen. Michael Flynn to resign in response to an “erosion” of trust between the two.

“The issue pure and simple came down to a matter of trust and the president concluded that he no longer had the trust of his national security adviser,” Spicer said during the White House press conference on Tuesday. He also revealed that there was “a series of other questionable instances” that also contributed to the erosion of the president’s trust.

Spicer said that Trump was “concerned” about Flynn after it was clear that he had misled the Vice President about phone conversations with his Russian counterparts about sanctions.

After the Justice Department notified the White House counsel that they had evidence Flynn was not telling the truth, Spicer confirmed that they investigated the legal ramifications of his actions. Spicer revealed that the Justice Department didn’t notify the administration about their knowledge of the calls until January 26, nineteen days ago.

Spicer added that Flynn’s actions were not illegal, as determined by the White House counsel, but it created what he called an “unsustainable situation.”

“That’s why the president decided to ask for his resignation, and he got it,” Spicer added.