BEDMINSTER, N.J. – President Donald Trump's acting secretary of Homeland Security expressed regret Sunday for the timing of immigration raids that netted 680 workers at food processing plants in Mississippi, an operation that took place after a mass shooting that targeted Hispanics in El Paso, Texas.

"The timing was unfortunate," acting Secretary Kevin McAleenan said on NBC's "Meet The Press."

McAleenan said the long-planned raid received court approval before the operation that led to the arrests of 680 people, the majority of them Hispanic.

"That means those employers are just ignoring the law entirely in what they do," McAleenan said. "That's why a judge gave us a warrant to go after them."

McAleenan said the administration is aware that Hispanics feel targeted in the wake of the mass shooting Aug. 3 in El Paso that claimed at least 22 lives, days before the raids in Mississippi.

The Department of Homeland Security regards the El Paso shooting as an attack "on our community" at the U.S.-Mexican border and is working to address the threat of "domestic terrorism," McAleenan told NBC News.

Asked whether authorities considered delaying the raids conducted by U.S. Immigration and Customs Enforcement, McAleenan said, "Something like this has been planned for over a year. This is a criminal investigation with 14 federal warrants issued by a judge, and ICE had to follow through on that. It was already planned and in motion.”

Only employees were arrested at the plants – not employers.

Officials said Thursday that 300 people arrested during the raids were released.

More:'They're going to lose everything': Families are devastated after Mississippi ICE raids

"We're in the middle of an ongoing investigation," McAleenan said. "You get a warrant from a federal judge with probable cause. You then go gather evidence at the sites. And then you look at the appropriate charges in concert with the Department of Justice and U.S. attorney to see how you proceed."

Congressional Democrats said they are looking into events that led up to the raids in Mississippi.

In a letter to Matthew Albence, acting director of ICE, Rep. Bennie Thompson, D-Miss., lamented that the raids stranded children of the workers who were arrested.

"At a time when this country is grieving due to two domestic terrorist shootings, your agency has instead seemingly deliberately disregarded its own long-standing guidelines and carried out another form of family separation," Thompson said.

After the attack in El Paso, another mass shooting that weekend in Dayton, Ohio, killed nine people.

"The blatant lack of planning and resulting chaos calls into question the true motivation behind these worksite enforcement operations," Thompson said.

Mark Morgan, acting commissioner of U.S. Customs and Border Protection, defended the operation on CNN's "State of the Union."

"We still have to apply consequences, meaning enforce the rule of law, for those individuals that are here illegally against immigration law," he said.