Kirstjen Nielsen’s replacement as Homeland Security secretary was practicing law in California when hijacked jets struck the World Trade Center and Pentagon on Sept. 11, 2001. That night, he applied for a job with the FBI.

“I was trying to pay off student loans and then go for a federal career but decided it couldn’t wait,” Kevin McAleenan told The Associated Press in 2017.

Robert C. Bonner, the new head of what was then called the U.S. Customs Service, got to McAleenan before the FBI and asked him to move to Washington to help set up an anti-terrorism office. A series of promotions over the next 18 years at what is now called Customs and Border Protection culminated Sunday when President Donald Trump named McAleenan to serve as acting Homeland Security secretary, when Nielsen leaves office later this week.

It is in some ways an unusual choice. Trump and his supporters have railed against both Obama administration policies and career government officials. But in picking McAleenan, Trump will have as his point person on politically charged border issues someone who served as a top Obama administration immigration official, in addition to serving under President George W. Bush.

Yet McAleenan appears to have endeared himself to Trump, who tweeted Sunday “I have confidence that Kevin will do a great job!” While avoiding fire-breathing ideological rhetoric and keeping a relatively low profile, McAleenan played a critical role executing some of Trump’s most controversial policies. As Customs and Border Protection commissioner, he helped put in practice a “zero tolerance” policy on illegal entries that caused thousands of children to be separated from their families at the border. He also oversaw the rapid spread of a practice to limit the number of asylum seekers who can enter the country at border crossings with Mexico, which he blames on processing constraints.

He has also shown strong interest in understanding why large numbers of Central American families are coming to the U.S., traveling to Guatemala’s western highlands last year on a fact-finding mission. He put renewed emphasis on providing medical attention to migrants after two Guatemalan children died in U.S. custody.

But McAleenan angered many Democrats when he didn’t mention the death of one of those children, a girl, during congressional testimony last year. Rep. Joaquin Castro, a Texas Democrat and chairman of the Congressional Hispanic Caucus, said he called for McAleenan’s resignation after the omission, which McAleenan said was an effort to avoid politicizing the little girl’s death.

“He cannot be trusted as Acting DHS Secretary based on his record of prioritizing Trump’s harmful policies that undermine national security and the economy, and hurt vulnerable families and children at the border,” Castro said. “The Hispanic Caucus will continue to hold the Trump Administration accountable for its actions against immigrants and against the will of the American people.”

Still, McAleenan was confirmed as Customs and Border Protection commissioner on a 77-19 Senate vote last year and has won praise from former colleagues and politicians across the political spectrum for his sharp intellect. As commissioner, he oversaw 60,000 employees and managed an annual budget of more than $13 billion.

“Kevin is a true patriot,” said Gil Kerlikowske, Customs and Border Protection commissioner from 2014 to 2017 and former police chief in Seattle and Buffalo, New York. “He’s incredibly smart, he’s got a great intellect, he’s very thoughtful, and he has a level of integrity and honesty that is very impressive. In my whole career, I can probably count on one hand the number of people that I’ve worked with that have reached Kevin’s level in all of those areas.”

Jay Ahern, acting head of Customs and Border Protection in the administration of George W. Bush, said McAleenan is a quick study who can recall important data when he needs it. He praised McAleenan’s humility as border chief.

“You want someone who has a certain amount of compassion for the people they encounter,” Ahern said. “You have to have that humanitarian side to be a leader for this.”

That may be at odds with the president’s hardline policies, Ahern said, but “Kevin has the ability to be very flexible and understanding of the political direction and can strike that right balance.”

McAleenan says was influenced at University of Chicago Law School in the 1990s by a professor, Gidon Gottlieb, who warned that that the U.S. was ill-prepared for a terrorist attack.

“He pounded the table and basically said we’re waiting for a Pearl Harbor-style terrorist attack,” McAleenan told the AP. “He was right, unfortunately.”

After working on counterterrorism issues, he supervised Customs and Border Protection operations at Los Angeles International Airport from 2006 to 2008 — “the best job I’ll ever have,” he said in the 2017 interview. From there, he steadily climbed the ranks.

White House spokesman Hogan Gidley said Monday that McAleenan is “extremely knowledgeable” and wants to work with Trump to put the president’s policies into effect.

“There’s no daylight between the two of ’em,” Gidley said on Fox News Channel. “We’re happy to work with him.”

(AP)