Rex Tillerson is out as secretary of state, the White House announced on March 13 as he came back to the U.S. from a trip to Africa.

Tillerson will be replaced as the nation’s top diplomat by CIA Director Mike Pompeo.

Rumors that Tillerson would be out as secretary of state have been circling for quite some time, and he was expected to step down from the position in January.

Tillerson told reporters that his last day will be March 31. Until then, he will delegate all of his responsibilities to the deputy secretary of state.

In leaving, Tillerson lamented that Washington, D.C., can be a "very mean-spirited town." He told the State Department employees that "personal integrity" is the "most valuable asset you posses."

Here’s a look at who Tillerson is and what he did before joining the ever-evolving Trump administration.

Who is Rex Tillerson?

Tillerson, 65, grew up in Texas and Oklahoma. He graduated from the University of Texas at Austin, where he earned a bachelor of science degree in civil engineering.

Tillerson is also known for his involvement with the Boy Scouts of America. He served as the organization's national president from 2010 to 2012.

Following the oft-criticized speech Trump gave to the Boy Scouts in 2017, Tillerson reportedly threatened to resign from the State Department.

What about his resume?

Prior to becoming secretary of state, Tillerson did not have any experience in the public sector.

Tillerson was the chairman and CEO of ExxonMobil until 2016. He served in that role starting in 2006, but he actually joined the company in 1975 as a production engineer, according to an archived version of his Exxon biography.

What has he done as secretary of state?

Tillerson’s tenure as secretary of state was fairly contentious with Trump. He reportedly called Trump a “moron” in front of other Cabinet officials in July 2017. Following reports of the remark, Tillerson gave an unusual personal address and reassured people he was not quitting.

As secretary of state, Tillerson traveled extensively – visiting Australia, Europe, Mexico and Africa, among other places. He assumed the position of secretary of state on Feb. 1.

Tillerson’s ties to Russia have also been scrutinized – a criticism that has plagued many Trump administration officials as investigators continue to look into Russian meddling in the 2016 election.

Tillerson was named vice president of Exxon Ventures (CIS) Inc., and president of Exxon Neftegas Limited in 1998. In those roles, Tillerson was tasked with overseeing Exxon’s holdings in Russia and the Caspian Sea, his Exxon biography stated. He met with Russian President Vladimir Putin multiple times before becoming secretary of state.

The Associated Press contributed to this report.