Washington — As soon Acting Homeland Security Secretary Kevin McAleenan took the stage to address a conference in Washington on Monday, he was a greeted by a chorus of fervent chants from a small group of pro-immigrant protesters, who listed some of the migrant children who've died in his agency's custody in recent months.

After chanting each name, the demonstrators yelled "presente," Spanish for present. Among the names chanted by the activists were those of Jakelin Caal Maquin, Felipe Gómez Alonzo and Carlos Gregorio Hernandez Vasquez — all Guatemalan children who have died in the custody of Border Patrol.

Despite the chants, McAleenan tried several times to continue his scheduled keynote address at the Migration Policy Institute's annual conference Monday morning to no avail.

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"As a career law enforcement professional, I've dedicated my career to protecting the right to free speech and all the values we hold dear in America — from all threats," the secretary told the crowd before being interrupted yet again.

"Bulls**t," one man in the audience yelled.

Acting Homeland Security Secretary Kevin McAleenan takes the podium at a immigration law and policy conference, Monday, October 7, 2019, in Washington. AP

At this point, McAleenan grew visibly frustrated and signaled to the hosts that he would leave. But organizers again asked the protesters to let the secretary finish his remarks and then have the chance to ask him probing questions about his busy and often tumultuous interim tenure at the helm of the sprawling Department of Homeland Security.

McAleenan agreed to try one more time, but he warned it would be his last attempt.

"When immigrants are under attack, what do we do?" one woman said, interrupting McAleenan. "Stand up. Fight back!" the rest of the protesters responded.

The secretary thanked the hosts and walked out of the auditorium.

"The First Amendment guarantees all Americans the right to free speech and assembly," the Department of Homeland Security said in a statement following the incident. "Unfortunately that right was robbed from many who were scheduled to speak and attend today's event at Georgetown."

Protestors did not allow @DHSMcAleenan to start his scheduled remarks at the annual @MigrationPolicy conference in Washington. Listing the names of migrant children who have died in U.S. custody, they chanted “¡presente!” McAleenan walked out and did not give his speech. — Camilo Montoya-Galvez (@camiloreports) October 7, 2019

The Migration Policy Institute said it regretted that McAleenan's remarks were interrupted. The group, a nonpartisan think tank, issued a statement saying a democracy requires dialogue between "all sides on public policy issues," especially from high-ranking administration officials who play a major role in devising and implementing policy.

"By drowning out the Secretary's remarks, the protesters deprived immigration attorneys, service providers, journalists, advocates, business leaders, law students, and many others in the public who were in the audience from hearing his point of view and engaging in a meaningful dialogue," the group wrote.

Acting Homeland Security Secretary Kevin McAleenan seen July 26, 2019. Reuters

Unlike the acting heads of the immigration agencies at DHS — who are all unabashed in their frequent praise of President Trump and his immigration agenda — McAleenan has kept a relative low profile since assuming the post in April, distancing himself from inflammatory rhetoric and focusing much of his tenure on leading diplomatic engagements with countries in Latin America where the bulk of U.S.-bound migrants are coming from or transiting through.

In addition to the asylum agreements he has recently reached with countries in Central America, McAleenan has also overseen controversial policies to deter migration at the U.S.-Mexico border, including a program that has required more than 50,000 asylum seekers to wait in Mexico for the duration of their court proceedings and a regulation allowed by the Supreme Court that renders most migrants ineligible for asylum if they traveled through a third country to reach the U.S.

In May, McAleenan's first full month on the job, border apprehensions reached a 13-year monthly high. In the past three months, however, apprehensions of border-crossing migrants have steadily declined.