WASHINGTON (AP) — Interior Secretary Ryan Zinke says in his resignation letter to President Donald Trump that “vicious and politically motivated attacks” on him and his family have “created an unfortunate distraction” in fulfilling the agency’s mission.

Zinke is citing what he calls “meritless and false claims” and says that “to some, truth no longer matters.”

The Associated Press obtained the letter after Trump had tweeted Saturday that Zinke would leave the Cabinet post at year’s end.

The former Montana congressman is facing federal investigations into his travel, political activity and potential conflicts of interest.

Zinke says all allegations have been investigated thoroughly, and he writes that “in each matter the conclusion has been and always will be that I follow all rules and regulations.”