A U.S. Border Patrol agent shot and killed a migrant near the Mexican border in Texas, U.S. Customs and Border Protection said Thursday.

The agent was responding at about 12:30 p.m. (1:30 p.m. ET) Wednesday to a report of "illegal activity" near a culvert in Rio Bravo, in Webb County about 10 miles south of Laredo, when he encountered a group of migrants, according to Customs and Border Protection.

"Initial reports indicate that as the agent attempted to apprehend the group, he came under attack by multiple subjects using blunt objects," the agency said in a statement.

The agent fired at least one round and fatally shot one of the migrants, according to the agency, which said three people whom it described as "illegal aliens" were arrested. It didn't identify the officer or the shooting victim.

Marta Martinez, who lives near the scene, said that she heard the shot and began recording video on her cellphone. She told NBC affiliate KGNS of Laredo that the victim was a young woman.

In the video, which Martinez posted to Facebook, people in uniform can be heard yelling, apparently at the migrants, "See what happens?" and "See what you caused?"

Martinez said she was shocked by the events.

"They come here to the United States to live the American dream," she told KGNS. "So there's no American dream right there. She died right there on the scene."

The FBI and the Texas Rangers are investigating, Customs and Border Protection said. Authorities scheduled a news conference for Friday.

The shooting comes as President Donald Trump has been ramping up his rhetoric about illegal immigration. In a speech last week in Washington, the president referred to some people who cross the border illegally as "animals."

Border Patrol agents were involved in 17 use-of-force cases with firearms in the fiscal year that ended Sept. 30, the last full year for which complete data are available, Customs and Border Protection reported.

That was down from 26 during the same period the previous year and from a high of 55 in 2012, according to the agency's data.