Reginald Brown, a veteran Washington attorney known for counseling corporations and executives through investigations and crisis management, is leaving the law firm Wilmer Cutler Pickering Hale and Dorr for Kirkland & Ellis.

For Brown, the move ends a 15-year tenure as a partner at Wilmer, where he led the firm’s financial institutions practice and had become an in-demand adviser for executives preparing for high-profile congressional hearings. Among his notable clients is Facebook CEO Mark Zuckerberg, who turned to Brown as he was summoned to Capitol Hill for closely watched hearings addressing everything from the social media company’s content moderation and efforts to sift out misinformation to the market dominance of tech giants.