Customs and Border Protection Commissioner Kevin McAleenan appears before the Senate Judiciary Committee on Dec. 11. (Jabin Botsford/The Washington Post)

U.S. Customs and Border Protection Commissioner Kevin McAleenan told senators Tuesday that his agents’ use of tear gas last month to stop a mass illegal crossing was a justified response to an “assaultive” crowd, and said the United States continues to face a “border security and humanitarian crisis” because so many Central American families and children continue to arrive seeking asylum.

Testifying before members of the Senate Judiciary Committee, McAleenan fielded questions on an array of enforcement topics, from the separation of children from their parents at the border this year to border wall cost projections and sweeping demographic changes in the composition of those taken into custody by U.S. agents.

When asked by Sen. Dianne Feinstein (Calif.), the committee’s top Democrat, whether CBP agents and officers targeted children with tear gas Nov. 25, when hundreds of people in Tijuana rushed toward the border in a chaotic melee, McAleenan told her “absolutely not.”

“We did not target young children,” he said, insisting that agents responded with gas and pepper ball rounds after “agitators” threw rocks at them in an attempt to force their way through the border. CBP said last month that four of its agents were struck by rocks but uninjured, but McAleenan said Tuesday that one agent ended up needing knee surgery.

The commissioner told senators that his agency is conducting a standard review of the use of force in the incident but that his agents acted in a manner consistent with their training. “I think it’s remarkable that agents were able to resolve the situation without any serious injuries or a breach of the border.”

On a day when President Trump invited television crews into the White House to broadcast his border wall negotiations with Democratic leaders, McAleenan said additional barriers would be an “important tool” to stop illegal crossings. But he urged senators to support investments in “the entire immigration continuum” and said his agency is seeking better technology and additional agents as well.

McAleenan reaffirmed Tuesday that CBP is not seeking to build a single 2,000-mile concrete barrier along the border with Mexico, and instead wants about 1,100 miles of “border wall system” anchored by steel bollard-style fencing that allows agents to see what’s on the other side.

The CBP commissioner declined to answer questions about negotiations with Mexico on a plan to require asylum seekers to remain outside the United States while their claims are processed, but he praised new President Andrés Manuel López Obrador’s proposal for increased development aid to Central America, and he said he was “very optimistic” about partnering with López Obrador’s leftist government.

Last month, migrants from Guatemala accounted for the largest number of border-crossers taken into custody, displacing Mexican nationals for the first time on record, McAleenan said, in one sign of what he described as an “unabated” increase in Central American families entering the country to seek humanitarian refuge.

Last month, CBP arrested or prevented from entering more than 62,000 migrants at the Mexico border, the highest one-month total since Trump took office.

McAleenan told lawmakers that his agents took more than 3,000 people into custody last Monday alone, the highest one-day total “in years.” Of those, 1,100 were children or underage minors, he said. 

U.S. Border Patrol stations have been primarily designed to process single male adults, not families with children, McAleenan told lawmakers, and he said he wants to bring more mental-health and medical professionals to provide proper care for those in U.S. custody. He described one Border Patrol station in El Paso with supplies of diapers and infant formula on hand, and children “in the office break room watching movies.” 

As CBP commissioner, McAleenan is in charge of the country’s largest federal law enforcement agency, with 20,000 Border Patrol agents and more than 23,000 blue-uniformed CBP officers stationed at border crossings, airports and other entry points.