Alex Villanueva sworn in Monday as Los Angeles County sheriff

LOS ANGELES (FOX11/AP) - Alex Villanueva was sworn in Monday as Los Angeles County sheriff, a week after scoring an upset victory that made Jim McDonnell the first incumbent to lose the seat in more than a century.

From Phil Shuman:

Alex Villanueva was almost overwhelmed by supporters, colleagues, family, and friends after his swearing in at East Los Angeles College this morning.

He's the 33rd Sheriff of Los Angeles County, running the largest department in the country, some 18,000 men and women, and administering a budget of some 3.5 billion dollars, huge by any standard.

He told FOX 11 he is happy, tired, excited and 'a bit overwhelmed.' When I asked him his top priorities he said he's already started ''cleaning house'' ( he's gotten rid of many top officials under his predecessor Jim McDonnell and already appointed an Asian and a woman as his top two assistants, and brought back some recently retired brass) and number two he said ''work on ICE."

The issue of ICE in the county jail is a hot button one, Sheriff McDonnell allowed ICE office space in the county jails if they were picking up criminals getting out of jail who had deportation orders, but Villanueva said ''no'' to that.

However, he said ICE can pick them up in the parking lots.

A technical distinction perhaps but he made it work.

A campaign mailer depicting him as a Democrat ( it's a non-partisan race ) facing off against an image of President Trump, then Attorney General Sessions and the back of an ICE agent certainly seemed to resonate with his supporters.

Kevin DeLeon , the State Senator who just lost a U.S. Senate race to Diane Feinstein , and author of so called the ''sanctuary state law'' told me he thought Villanueva won in part because of the ''Anti-Trump'' sentiment, but that it's more complex than that.

Villanueva 's pledge to the rank and file, who supported him, is that ''your success will be determined by how you serve the community, not the political powers that be.''

That line got huge applause at today's swearing in.

Earlier:

Villanueva, a retired sheriff's lieutenant, took the oath of office during a ceremony attended by deputies, community leaders and elected officials.

The 55-year-old will run the largest sheriff's department in the nation, overseeing nearly 10,000 deputies and 8,500 civilian personnel.

Last week, he vowed to make good on a campaign promise to clean house at the agency by dismissing more than a dozen people in leadership positions.

He further discussed his plans during an appearance on Good Day LA.

McDonnell promised an orderly transition of power in a statement on Nov. 26, nearly three weeks after the election. The race was initially too close to call, but Villanueva's lead steadily expanded.

McDonnell finally conceded after updated results showed Villanueva leading by more than 125,000 votes - with only 100,000 ballots left to be counted. The final tally gave Villanueva 53 percent of the vote.

Villanueva joined the sheriff's department as deputy after leaving the U.S. Air Force in 1986.