EPA Administrator Scott Pruitt on Thursday blamed the “unrelenting attacks” from his critics as the reason he decided to step down from his post, in a letter that thanked President Trump for the chance to serve in the post, but didn’t apologize for his various ethics scandals.

“The unrelenting attacks on me personally, [and] my family are unprecedented and have taken a sizable toll on all of us,” Pruitt said in his resignation letter to President Trump.