Transcript for 'I didn't like the sight': Trump signs executive order ending family separation

And we begin tonight with the stunning reversal. Late today, president trump signing an executive order that he says will keep families together and end the separation of children from their parents coming into this country illegally. It was just Friday when the president was asked, will he stop this? He said, we cannot do it through executive order. But that is exactly what he did today. The president saying he did not like the sight, after those images were seen for days by the nation, byhe world, children in cages. The audio of the children crying after being separated. All a result of the president's zero tolerance policy. As we heard the president today saying as he signed the order, "The I think the word compassion continues to mind." Tonight, the new questions here, did he need this executive order? Why didn't the president call his justice department days ago? ABC's senior white house correspondent Cecilia Vega leading us off again tonight. Reporter: In the oval office today, president trump did exactly what he said he could not do -- he ended his policy separating migrant families at the border with the stroke of a pen. We're going to keep the families together. I didn't like the sight or the feeling of families being separated. We're keeping families together, and this will solve that problem. Reporter: It is a stunning reversal. Just days ago -- You can't do it through an executive order. Reporter: And homeland security secretary kirstjen Nielsen insisting -- Congress alone can fix it. Reporter: Last night, Nielsen was shouted down by protesters as she dined at a Mexican restaurant. Shame! Shame! Shame! If kids don't eat in peace, you don't eat in peace! Reporter: And the president himself coming face-to-face with the outrage, as he walked the halls of congress. You're separating the children! Mr. President, don't you have kids? Reporter: Exactly 75 days after he began his zero tolerance crackdown, the crisis reaching fever pitch, after those images of children in cages. And the sounds of their cries. Today, news that babies are being held in facilities called tender age shelters. Veteran Republican senator or win hatch calling tender age shelters "A chilling phrase we will not soon forget." He tweeted, "The child separation policy should be halted now." The administration has struggled to explain its policy. Nielsen bristling when asked if the children were being used as pawns. Are you intending for parents to be separated from their children? Are you intending to send a message? I find that offensive. Why? No. Because why would I ever create a policy that purposely does that? Perhaps as a deterrent. No. Reporter: Hours later, she was contradicted by the attorney general. Is it a deterrent, sir? Are you considering it a deterrent? Yes. Hopefully people will get the message and come through the border at the port of entry and not break across the border unlawfully. Reporter: Thelames fanned by the president's former campaign manager's reaction on Fox News to the Mexican government's allegation that a girl with down syndrome was separated from her mother. I read today about a 10-year-old with down syndrome who was taken from her mother and put in a cage. Womp, womp. I read about -- did you say "Womp womp" to a 10-year-old with down syndrome? How dare you! Reporter: Today, president trump called it an impossible dilemma. He said his own wife and daughter were moved by the images. Sources tell us they both lobbied him to put an end to the policy, even as they now face widespread backlash, people calling them complicit. If you're really, really pathetically weak, the country's going to be overrun with millions of people, and if you're strong, then you don't have any heart. That's a tough dilemma. Perhaps I would rather be strong, but that's a tough dilemma. Reporter: Faced with mounting political pressure, this is how the president explained the reversal. I think the word compassion comes into it. But it's still equally as tough, if not tougher. And Cecilia Vega joins us live from the white house. Cecilia, president trump says the zero tolerance policy is still in effect tonight, but children and parents who enter the country illegally will be detained together, according to his executive order, as their cases are reviewed. But that leads to new questions. Among them, how long can trump administration detain entire families? Reporter: Well, for now, we know it's up to 20 days, David. But the white house is asking a judge to be able to go beyond that. So, these could potentially be long-term stays for these families. This executive order does allow for new construction for facilities to house some of these families. This is far from over, David. President trump said today that he is bracing for potential lawsuits. Cecilia Vega leading us off. It was last night here, we

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