Mark A. Morgan testifies at his first hearing on Capitol Hill as U.S. Border Patrol chief on Sept. 13, 2016. (Photo by Donna Burton/Customs and Border Protection)

The man who would be in charge of guarding a wall with Mexico if Donald Trump is elected president isn’t so sure the strategy would keep undocumented immigrants out.

Instead, Mark Morgan —  the first outsider to lead the 21,ooo uniformed agents who make up the U.S. Border Patrol — has had another priority in the three months he’s been on the job: changing the agency’s culture.

The law enforcement force on the front lines of U.S. border security has faced allegations of an overly confrontational approach that’s resulted in multiple fatal shootings, long unaddressed internal corruption and a lack of accountability in investigating misconduct.

Morgan has never arrested an illegal immigrant. But Customs and Border Protection Commissioner R. Gil Kerlikowske turned to him — overlooking others who came up through the ranks — to change course in what is, even by law enforcement standards, an insular culture.

“It was a culture of not getting out and talking about issues, not being transparent about the process that drove the perception there was a culture problem,” Morgan, a career FBI official and former Los Angeles police officer, said in his first interview since his appointment in June.

Besides meeting with line agents at almost half of the 20 outposts that cover 6,000 miles along the Southwest and Canadian borders, Morgan, 51, has spent his first weeks in the job ensuring that new use-of-force policies in the training academy curriculum are encouraging recruits to turn to other strategies to defuse encounters that could get violent.

He’s devising strategies to help agents develop better intelligence on the drug cartels and smugglers behind so many illegal crossings. He’s coordinating multiple law enforcement authorities so that if agents do fire their weapons, there is a system to review whether the action was appropriate.

“The border patrol comes into contact with a lot more people than the FBI,” he said in his Washington office, dressed in the green Border Patrol uniform and black boots, his graying hair in a crew cut.

“The piece we need to get better at when a shooting happens is, what happens now?” he said. “I don’t think we were very good at all about making decisions like whether the use of force was within our guidelines.”

When it comes to enhancing border security, the wall the Republican nominee for president has proposed to keep out illegal immigrants does not top Morgan’s list, however hotly debated it has been. As a civil servant and not a political appointee, Morgan will be in the job whether Trump or Hillary Clinton is elected.

“A simplistic answer to an immensely complex problem,” is how Kerlikowske describes the wall. He notes that the government “spends a tremendous amount of money repairing what we have now” on the Southwest border — 600 miles of very intermittent fencing — from damage from erosion, flooding and holes when migrants break through.

“Does infrastructure play a role? Of course,” Morgan said. “It’s one element of a multifaceted approach. It isn’t the answer.”

He quipped, “I try not to be in the business of sound bites.”

Morgan is, however, in the business of educating himself about the agents who patrol the border solo in scorching desert heat and frigid winters. He commutes an hour each way along Interstate 95 from his home in Stafford County, Va., where he spends most weekends poring over research and policy on training tactics, high-tech sensors and other border security strategies.

In his (limited) spare time, he remodels and putters, two hobbies he says he’s “pretty good at.” His reading list skews heavily toward books on leadership. He says they’ve taught him that “you don’t need to have a title to be a leader who makes an impact.”

Morgan’s varied FBI resume includes leading a Hispanic gang task force in Los Angeles and senior roles in Baghdad, New Haven, Conn., and El Paso. He was in charge of agency-wide training when Kerlikowske tapped him for the Border Patrol post, passing over several inside candidates.

Morgan was not entirely new to border security. Two years ago, Kerlikowske brought him in to run the internal affairs office at the larger Customs and Border Protection agency after removing the longtime official in the job. That official was criticized for failing to investigate multiple allegations that Border Patrol agents had used excessive force on migrants.

An review in March by the Homeland Security Advisory Panel, an oversight board, criticized the system of discipline for abusive or corrupt Border Patrol agents as “deeply flawed.”

Morgan is credited with bringing more accountability to these cases.

His appointment was criticized by the powerful Border Patrol union, which said an outsider could never gain agents’ trust. Today union spokesman Shawn Moran says agents “understand they’re going to give the new chief a feeling-out period.”

Moran said the public has “a lot of misconceptions that the Border Patrol is a trigger-happy organization rife with corruption.”

Kerlikowske said the problems stem from a “huge amount of growth” in the force since the terror attacks of Sept. 11, 2001, along with increasingly aggressive drug cartels and smuggling operations. “Now it’s not uncommon to see people carrying guns,” he said.

Asked to describe the state of border security at a time when Trump supporters decry a massive lack of it, Morgan said, “Everybody has a different perspective on that.” Some will say, of course, that the border is not secure unless you catch everyone who tries to cross illegally.

He acknowledges that it’s very hard to know how large this group is.

“How do you measure something you’re preventing?” he asks. “We’re constantly trying to improve the way we measure this.”