Department of Defense Rear Adm. Kevin Sweeney (Ret.) has stepped down as chief of staff to the secretary of defense.

The chief of staff to the secretary of defense, Rear Adm. Kevin Sweeney, has resigned, according to a news release issued Saturday.

No reason was given for Sweeney’s departure, which was announced five days after the formal departure of Defense Secretary James Mattis. Sweeney had been chief of staff since January 2017.

“After two years in the Pentagon, I’ve decided the time is right to return to the private sector,” Sweeney said in a statement following his decision to step down. “It has been an honor to serve again alongside the men and women of the Department of Defense.”

Sweeney isn’t the only departure. At the end of December, then Pentagon spokeswoman Dana White announced on Twitter that she would be leaving her post, too.

“I appreciate the opportunity afforded to me by this administration to serve alongside Secretary Mattis, our Service members and all the civilians who support them. It has been my honor and privilege,” she wrote in the Dec. 31 tweet. “Stay safe and God bless.”

No information was available on who may take Sweeney’s place.