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

It is effective May 11.

"We enforce the law without fear 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 endures is not governed by the news cycle."

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

After Comey was fired, Rosenstein brought Mueller in as special counsel to continue the investigation, and Mueller also looked at the question of obstruction of justice.