A senior deputy to FBI Director Kash Patel will depart the bureau after roughly one year on the job - news that comes as the preeminent law enforcement agency has struggled to respond to concerns of politicization.  

Andrew Bailey, a co-deputy FBI director, announced his departure in an email shared early Monday with bureau employees, and later, via a shorter statement shared on social media.

‘What I have observed during my time here … are focused, dedicated professionals who are prepared to do whatever is necessary to uphold the Constitution and protect the American people,’ Bailey said in an email announcing his resignation, which was shared with the Daily Mail.

Bailey closed his note to FBI staff saying he remained ‘forever grateful for the opportunity to serve this administration,’ and will ‘reflect with pride’ on his time at the bureau.

His last day at the FBI is Friday.

Bailey's departure comes as the FBI has come under mounting scrutiny in recent months for a wave of contentious decisions and personnel actions at the bureau.

That includes the mass purge of FBI agents tasked with investigating the January 6, 2021, US Capitol riot, and other investigations Trump had decried in the run-up to his second presidential election.

Bailey, who had been widely reported to be on Trump's short list of attorney general nominees at the start of his second term last year, is believed to have clashed with Patel over certain leadership decisions made at the bureau. 

Patel, for his part, sparred with Senate Democrats at an hours-long FBI oversight hearing earlier this month. 

The hearing was combative and personal as Patel sought to defend his fitness for the role amid reports of heavy drinking and his alleged use of FBI resources, including to serve as a security detail on occasion for his girlfriend, Alexis Williams. 

At times, the exchanges between Patel and Democrats on the panel devolve into full-on shouting matches. 

Patel accused Democrats on the panel of baselessly attacking him and his loved ones for their own political gain - while lawmakers, in response, accused Patel of filibustering and refusing to answer germane questions related to FBI oversight. 

'We have a lackey. And frankly, he's not even a good lackey,' Senator Cory Booker, a Democrat from New Jersey, said of Patel during the explosive hearing. 

'He's like an 18-year-old kid who wants to join a fraternity that he could never be a member of, doing keg stands and chugging with friends,' Booker continued of Patel, adding, 'He's an embarrassment to the agency - and wouldn't qualify even to be an FBI agent.'