Washington( CNN) Deputy Attorney General Rod Rosenstein, who appointed special counseling Robert Mueller to investigate Russian interference in the 2016 presidential election, submitted his resignation letter to the White House Monday.

“We enforce the law without anxiety or favor because credible evidence is not partisan, and truth is not determined by opinion polls, ” Rosenstein wrote. “We ignore fleeting distractions and focus our attention on the things that matter, because a republic that suffers is not governed by the news cycle.”

Rosenstein often procured himself the target President Donald Trump, especially after hiring Mueller in 2017. Shortly after being corroborated as deputy attorney general, Rosenstein wrote a memo criticizing former FBI Director James Comeyamid Comey's investigation into Russia's 2016 actions, which Trump used as part of his reasoning in firing Comey.