Le Duc's photo shows Martínez floating in the water with his daughter by his side, wrapped in his shirt and holding his neck.
>> See the photo here (WARNING: Graphic image. Viewer discretion advised.)
“He put her in his shirt, and I imagine he told himself, 'I've come this far' and decided to go with her," his mother Rosa Ramírez, who stayed in El Salvador, told the AP.
Last year, 283 migrants died along the U.S.-Mexico border, the AP reported.
Following the latest deaths, Alexandra Hill, El Salvador's minister of foreign affairs, urged residents of the Central American country to stay put, CNN reported (WARNING: Linked story includes disturbing photo).
"Our country is in mourning again," she said, according to the news outlet. "I beg you, to all the families, parents, don't risk it. Life is worth a lot more."
Trump told reporters Wednesday that the deaths were the fault of Democrats who refuse to change immigration laws.
“That’s like I’ve been saying -- if they fixed the laws you wouldn’t have that,” Trump said. “People are coming up, they’re running through the Rio Grande. It’s a rough -- It can be a very rough river of sorts, I mean there are times when going across the Rio Grande is very, very dangerous depending on the time of year and the conditions and the rapidity of the water, and we know that.”
Some 2020 Democratic presidential candidates, including Sen. Cory Booker, Sen. Kamala Harris and former U.S. Rep. Beto O'Rourke, expressed outrage on social media after seeing the photo.
"We should not look away," Booker tweeted Tuesday evening. "These are the consequences of Donald Trump’s inhumane and immoral immigration policy. This is being done in our name."
"These families seeking asylum after often fleeing extreme violence," Harris wrote. "And what happens when they arrive? Trump says, 'Go back to where you came from.' That is inhumane. Children are dying. This is a stain on our moral conscience."
O'Rourke tweeted that the president "is responsible for these deaths."
"As his administration refuses to follow our laws – preventing refugees from presenting themselves for asylum at our ports of entry – they cause families to cross between ports, ensuring greater suffering & death," O'Rourke wrote. "At the expense of our humanity, not to the benefit of our safety."
Trump Tweets Millions Living Illegally in U.S. Will Be Deported
Although the White House has not commented on the photo, Trump took to Twitter early Wednesday to blast Democrats' position on immigration.
"Too bad the Dems in Congress won't do anything at all about Border Security," he wrote, later adding: "Democrats want Open Borders, which equals violent crime, drugs and human trafficking. "
– The Associated Press contributed to this report.