GEOFF BENNETT: On a recent evening in Washington, moviegoers filled the lobby of a local theater to watch the D.C. premiere of a new film from a renowned documentarian that explores the first Trump administration's family separation policy on the U.S. southern border.

I recently sat down with one of the executive producers of the film, "Separated."

JONATHAN WHITE, Former Office of Refugee Resettlement Official: Systematic separation of children from parents, officially, it wasn't happening.

But it was happening.

GEOFF BENNETT: The new documentary "Separated," is a searing exploration of the first Trump administration's zero-tolerance immigration policy at the U.S.-Mexico border, which forcibly separated over 5,000 migrant children from their families who illegally entered the country.

Directed by the legendary documentarian Errol Morris the film is based on a book of the same name NBC News journalist Jacob Soboroff, who's also one of the film's executive producers.

One of the things that so often gets lost in conversations about Trump's family separation policy is that harm to children was the point.

JACOB SOBOROFF, NBC News Correspondent: It was the point.

GEOFF BENNETT: In fact, one of the civil servants who you speak with in the film says that.

It was meant to terrify parents from making that trek from those Northern Triangle countries to the U.S. JACOB SOBOROFF: Based on the facts that we know, which in this film are firsthand interviews with civil servants who tried to stand up and stop the policy and in fact help the policy reversal, we know what they wanted to do.

They wanted to hurt kids in order to scare other families from coming to this country and scare Congress into enacting more restrictive immigration laws.

It's exactly the way that they drew it up and exactly what they wanted to do.

GEOFF BENNETT: One of the civil servants who offers a firsthand account is Jonathan White, who worked for the Office of Refugee Resettlement.

JONATHAN WHITE, Former Office of Refugee Resettlement Employee: And the unaccompanied children program, which I worked in, was essentially hijacked for a purpose for which it was never intended, nor authorized in law.

It was a program designed to be a child protection program for children who entered the United States without parents.

And it was instead used as a tool to take children from their parents.

GEOFF BENNETT: Since there's no footage of the actual family separations, the film includes narrative vignettes depicting the forced separation of a mother and son who illegally crossed the border.

One of the questions I had during this entire process, the family separation process, was like, what about the guards?

What about the people who worked at these facilities?

What about the civil servants who were really tasked with overseeing this process, separating infants from their parents?

How did they grapple with this?

JACOB SOBOROFF: You know, many of them carried out the orders and many of them didn't stand up in protest, but some of them did and they spoke out, and especially within the Department of Health and Human Services.

GEOFF BENNETT: Soboroff says it was career staffers like White and his co-worker Jallyn Sualog who pushed to reverse the policy and later faced the difficult task of reuniting children with their parents, since there was no formal process of tracking family separations.

JALLYN SUALOG, Spoke Out Against Family Separations: When you have a 2-year-old, their assessment form in the system doesn't have that much information.

"What's your mom's name?"

"Mom."

Like, every mom, their name is Mom.

GEOFF BENNETT: And he connects Trump's policy to decades of punitive immigration laws enacted under both Republican and Democratic administrations.

JACOB SOBOROFF: Bill Clinton built the first wave of border walls.

George W. Bush exponentially increased the size of the Border Patrol, created DHS in the wake of 9/11.

Barack Obama deported more people than any president in the history of the United States of America.

They called him the deporter in chief.

And that's why, like that, Donald Trump was able to take away 5,500 children from their parents in an act that a Republican-appointed judge called one of the most shameful chapters in the history of our country.

GEOFF BENNETT: So it was the systematic separation of children that was new, the fact that there were these state-created orphans; that was new under Trump?

JACOB SOBOROFF: A hundred percent.

And I hear often from people back then and even today saying, well, Obama did this or this happened under Biden, point a finger in every direction.

There never was until 2017, when the pilot program was implemented in El Paso, a deliberate and systematic attempt to rip parents and children apart from one another as United States immigration policy.

And there hasn't been since.

GEOFF BENNETT: He says the Biden administration failed to take action that might prevent it from happening again.

President Biden, he had called the practice of family separations criminal, promised a thorough investigation.

To this day, no one has been held accountable.

Why?

JACOB SOBOROFF: I remember you in some of those press conferences pressing on this exact topic.

GEOFF BENNETT: During the campaign, you said that practice was criminal.

Can you commit, will you commit to making sure that the Trump administration officials responsible for that policy will be held to account?

JOE BIDEN, President of the United States: I will commit that our Justice Department and our investigative arms will make judgments about who is responsible, how they're responsible, and whether or not the conduct is criminal.

But there will be a thorough, thorough investigation of who's responsible.

JACOB SOBOROFF: What's been done to this day is absolutely nothing.

Nobody's been held accountable for the policy.

Some of the people responsible for it are going to be in some of the most senior positions in the incoming Trump administration.

Immigration in the eyes of the Biden administration became a political liability.

And so they backed away.

They backed away from financially compensating these families.

They backed away from any idea of a criminal prosecution of people responsible for it.

And I think history will remember that.

GEOFF BENNETT: President-elect Donald Trump signaled he would declare a national emergency and use the U.S. military to carry out mass deportations of undocumented immigrants when he takes office.

There's been so much outrage fatigue since then.

Trump has already promised mass deportations.

But if we see a policy that is very similar to the family separation policy, I mean, how do you think the American public will respond?

JACOB SOBOROFF: Mass deportation is family separation by another name.

It's not ripping away children from their parents at the border, but it is taking parents away from children in their homes and at their schools and in the interior of the country.

I think when, they're reminded of what that really means, the American people will respond in the same way that they did to family separation, because it's not about politics.

It's about people.

GEOFF BENNETT: What do you want people to take away from this film as they watch it?

JACOB SOBOROFF: That people remember their power and how people stood up in that moment in the summer of 2018 and forced the Trump administration to stop something that was universally condemned.

And as we go into yet another Trump administration, where they're talking about doing a policy that would be orders of magnitude greater when it comes to disrupting the lives of immigrants in this country, if indeed it turns out to be family separation by another name again, people still have that power.

MAN: It troubles me profoundly that it could happen again,.

GEOFF BENNETT: "Separated" has been screened in select theaters across the country and airs on MSNBC on December 7.