WASHINGTON (AP) — Todd Lyons, the acting head of Immigration and Customs Enforcement, defended his agency's officers before Congress on Tuesday, standing behind their tactics and saying they would not be intimidated as they carry out the president's mass deportation plans.

Lyons was one of the three heads of agencies implementing President Donald Trump's immigration agenda to testify in a hearing called after the shooting deaths of two Americans at the hands of federal officers. They faced fierce questioning from Democrats, and support from most Republicans, over how they are prosecuting immigration enforcement inside American cities.

"Let me send a message to anyone who thinks they can intimidate us. You will fail," said Lyons, who blamed elected officials and protesters for escalating rhetoric that he said endangered his officers. Lyons, who at various points declined to comment directly on the killings of the two U.S. citizens, said his officers would not be deterred.

"We are only getting started," he said in opening remarks.

Trump's immigration campaign has been heavily scrutinized in recent weeks, especially after the shooting deaths in Minneapolis. The agencies have also faced criticism for a wave of policies that detractors say trample on the rights of both immigrants facing arrest and Americans protesting the enforcement actions. Tuesday's testimony is unlikely to quell simmering tensions over the centerpiece policy of Trump's second term.

Lyons, the acting ICE director, Rodney Scott, who heads U.S. Customs and Border Protection, and Joseph Edlow, who is the director of U.S. Citizenship and Immigration Services, spoke in front of the House Committee on Homeland Security in a hearing that lasted roughly three and a half hours.

Agency leaders testify as DHS faces a funding lapse

This is the first time all three have appeared in Congress since the department received a huge infusion of money from Congress last summer and since immigration enforcement operations intensified across the country.

Under Lyons' leadership, ICE has undergone a massive hiring boom and immigration officers have deployed in beefed-up enforcement operations designed to increase arrests and deportations.

The officials spoke at a time of falling public support for how their agencies are carrying out Trump's immigration vision. Their testimony comes as Democratic lawmakers in Congress are demanding restraints on immigration officers before agreeing to fund the Department of Homeland Security. The agency heads warned the country would be less safe if federal funds expire at the end of the week.

Tuesday's hearing was called after federal officers shot and killed Alex Pretti and Renee Good, which sparked outrage across the country and demands for accountability and reform. Lyons and Scott said standard operating procedures were being followed in investigations into the January shootings.

Tensions flared and the hearing sparked heated exchanges -- the Democrats comparing the enforcement operations to Nazi Germany and questioning how the administration officials will be judged -- the chairman at times gaveling the lawmakers back to order.

The ranking Democratic member of the committee, Rep. Bennie Thompson of Mississippi, called the hearing the "start of a reckoning" and said Homeland Security Secretary Kristi Noem should be held accountable. Thompson said the department has blocked lawmakers from visiting detention facilities and needs to be more responsive to questions.

"Every American should be outraged," Thompson said.

Republicans shifted attention back to Biden-era policies, which allowed countless migrants to enter the country, and said the Trump administration has sealed the U.S.-Mexico border and is ending a "lawlessness" in the nation's immigration system.

Trading blame over the growing tensions

Opening the hearing, Rep. Andrew Garbarino, chairman of the committee, called the moment an "inflection point." The New York Republican said the deaths of the two U.S. citizens were "unacceptable and preventable."

The administration says that activists and protesters opposed to its operations are the ones ratcheting up attacks on their officers, not the other way around, and that their immigration enforcement operations are making the country safer by finding and removing people who've committed crimes or pose a threat to the country.

Scott lashed out at what he called an "unprecedented level of aggressive interference and intimidation" against federal officers in the course of doing their jobs, calling "attacks" on federal officers "coordinated and well funded."

Since Trump returned to the White House, Customs and Border Protection has taken on a significant role in arresting and removing illegal immigrants from inside the country. That increased activity has become a flashpoint for controversy and marks a break from the agency's traditional job of protecting borders and controlling who and what enters the country.

Rare pushback from Republican member

One Republican member of Congress suggested that it was Border Patrol commander Gregory Bovino who had contributed to the escalation in tensions over immigration enforcement, especially in Minneapolis.

"I would argue, in fairness, that he escalated the situation," Rep. Michael McCaul of Texas said.

Under Bovino, a group of Border Patrol agents hopscotched around the country to operations in Los Angeles, Chicago, Charlotte, North Carolina and New Orleans where they were often accused of indiscriminately questioning and arresting people they suspected were in the country illegally. Bovino says his targets are legitimate and identified through intelligence and says that if his officers use force to make an arrest, it's because it's warranted.

A Border Patrol agent and Customs and Border Protection officer both opened fire during Pretti's shooting death. Good was shot and killed by an ICE officer.

After the Pretti shooting, Bovino was reassigned and Trump sent border czar Tom Homan to Minneapolis to assume control, a move McCaul praised.

Lyons said that de-escalation was because protests had diminished, allowing ICE "to do their targeted, intelligence driven enforcement operation."

Lyons won't make officers take off masks

A key point of tension in Congressional debates over the president's immigration agenda has been whether officers should be allowed to wear masks while carrying out their jobs. Democrats are pushing to make officers take off the masks as part of budget negotiations.

Rep. Tim Kennedy, a Democrat from New York, asked Lyons if he would commit to making his officers take off their masks. Lyons answered, "No," which Kennedy called a "sad response."

Republican Rep. Ryan Mackenzie of Pennsylvania, asking Lyons about allegations that American citizens were being caught up in immigration enforcement operations, said greater transparency in DHS operations would be beneficial.

Lyons said he was committed to transparency, pointing to his support for officers to be outfitted with body cameras. He and Scott said thousands of officers deployed now wore them, with more to come.

Noem said last week that every DHS officer on the ground in Minneapolis would immediately be issued those cameras and that the program will be expanded nationwide as funding becomes available.