A Border Patrol agent shot and killed a migrant woman Wednesday in the Texas town of Rio Bravo, setting off an investigation over whether the use of force was justified.

The woman, who has not been publicly identified, was traveling with a group of unauthorized immigrants through the border town outside Laredo when a Border Patrol agent confronted them after receiving reports of “illegal activity,” according to Customs and Border Protection. When the agent tried to apprehend them, some in the group resisted using “blunt objects,” CBP said Thursday.

The agent, who has been with Border Patrol for 15 years, said the group refused to get on the ground and instead rushed at him, CBP said in a second statement on Friday. The agent fired at least one round that struck the woman in the head and killed her.

After the shooting, the agent called for emergency medical services and administered first aid to the woman, according to CBP. Three other unauthorized immigrants on the scene were apprehended later.

The FBI and Texas Rangers are investigating the shooting. CBP did not specify whether the three immigrants are in immigration custody slated for deportation or whether they will remain in the U.S. during the investigation.

News of the shooting circulated widely after a local resident filmed the aftermath and uploaded it to Facebook. “Why did you shoot at the girl? You killed her!” the woman who filmed the encounter says in Spanish as she approached Border Patrol agents at the scene in the video. “She wasn’t doing anything.”

The footage appears to show that shooting took place in a neighborhood street.

Viewers had watched the video 3.5 million times by midday Thursday.

While the details of Wednesday’s shooting remain unclear, it highlighted the need for greater accountability, said John-Michael Torres who is with LUPE, a south Texas advocacy group that works with immigrants.

“One of the big concerns for us is that Border Patrol has avoided so many accountability measures that other law enforcement agencies have adopted, like body cameras,” Torres said. “So when they tell us information about an incident like this, how do we believe what they say?”

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Since the beginning of 2017, there have been at least two other reported fatal shootings by officers on duty. In November, a CBP agent shot and killed a suspected unauthorized immigrant, who the agency claimed wrested control of another agent’s gun. In September, Border Patrol agents shot and killed a man after a car pursuit and exchanges of gunfire, CBP said. At least seven people have been killed in car accidents since the beginning of 2017 while fleeing border agents.

CBP reported 17 instances of use of force involving firearms in the 2017 fiscal year and 979 incidents not involving them. The previous year, there were 26 incidents involving firearms and 947 involving other use of force, according to CBP.

Border Patrol reported a massive increase in assaults against agents in the 2016 fiscal year, but The Intercept revealed the tally was based on highly unusual counting methods. One incident involving seven Border Patrol agents was counted as 126 assaults.

President Donald Trump is seeking to dramatically expand Border Patrol in a broad crackdown on unauthorized immigration. He ordered the hiring of 5,000 additional agents as Border Patrol struggles with retention problems and the fact that most applicants fail their background checks.

Karina Alvarez, a DACA recipient who helped found the community group Laredo Immigrant Alliance, told HuffPost that incidents like Wednesday’s shooting undermine local confidence in law enforcement, especially in light of the president’s ongoing hostile comments about immigrants.

“Laredo is very safe ― we don’t need a massive amount of border patrol or national guard,” Alvarez said. “They see us as animals. And it’s very frightening to live in a border town now.”

This article has been updated to include information from a second statement from Customs and Border Protection.

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This article originally appeared on HuffPost.