• Chris Magnus resigned as chief of Customs and Border Protection on Saturday, per the White House.
• Magnus had initially declined to step down from his position after being told by Mayorkas to do so.
• Magnus' departure comes after a year of record migrant apprehensions at the southwestern border.

The commissioner of Customs and Border Protection on Saturday resigned from his position, according to the White House, with the departure occurring after a year of record migrant apprehensions at the US-Mexico border.

President Joe Biden has accepted the resignation of Chris Magnus, who had served less than a year in the role.

"President Biden appreciates Commissioner Magnus' nearly forty years of service and the contributions he made to police reform during his tenure as police chief in three US cities," White House press secretary Karine Jean-Pierre said in a statement. "The President thanks Mr. Magnus for his service at CBP and wishes him well."

Magnus had initially declined to step down from his position after being previously asked to do so by Homeland Security Secretary Alejandro Mayorkas, which he relayed to The Los Angeles Times in an interview.

"I expressed to him that I felt there was no justification for me to resign when I still cared deeply about the work I was doing and felt that that work was focused on the things I was hired to do in the first place," Magnus told the Times.

On Saturday, Jean-Pierre included in the White House statement a copy of Magnus' resignation letter.

"Thank you for the opportunity to serve as your Senate confirmed Commissioner of US Customs and Border Protection over the past year. It has been a privilege and honor to be part of your administration," the letter read. "I am submitting my resignation effective immediately but wish you and your administration the very best going forward."

Mayorkas on Saturday issued a letter to Customs and Border Protection staffers confirming that Magnus had departed the agency and informing the workforce that deputy commissioner Troy Miller would be the acting commissioner effective immediately.

"We are thankful to Commissioner Magnus for his contributions over the past year and wish him well," Mayorkas wrote in his letter.

Magnus, the former police chief in Richmond, Calif., and Tucson, Ariz., had overseen over 60,000 employees who were largely focused on border security and counterterrorism issues.

He was confirmed to the role by the Senate in December 2021 in a 50-47 vote.

According to NBC News, the rift between the Biden administration and Magnus came into view after the publication of a recent Politico report that detailed how five administration officials "portrayed him as unengaged in his job, saying he often doesn't attend White House meetings on the situation on the border, badmouths other agencies to colleagues and superiors, and has not built relationships within CBP and across other agencies to address the influx of migrants at the border."

In a statement, Magnus responded at the time that he was "closely involved in the major DHS immigration, border security, trade, and other policy discussions," but also noted that he needed several months to get acquainted with the department's "many complex areas."

Border security has become a major issue for Biden, with Republicans and even some Democrats needling the administration over the level of undocumented migrants being caught by agents.

Texas Gov. Greg Abbott has sent migrants to Democratic-led cities including Chicago and New York to protest what he has repeatedly said is the federal government's lax security at the border.

Florida Gov. Ron DeSantis has taken a similar lead and has chartered flights to send migrants from Texas to Martha's Vineyard, Mass.

In the fiscal year that ended on Sept. 30, there were almost 2.4 million migrant arrests at the southwestern border, the highest number on record, according to data from the US Border Patrol.