The U.S. Border Patrol says an agent was trying to detain some people whom he suspected had entered the country illegally when they attacked him and he shot and killed one of them.

Border Patrol says the unidentified agent was investigating a report of illegal activity Wednesday in Rio Bravo, just south of Laredo, when he came across the group.

The agency said in a statement Thursday that the agent was trying to take them into custody when some attacked him “using blunt objects.” The agent fired at least once, striking one of his assailants. Three others who fled were apprehended by responding agents.

The FBI and Texas Rangers are investigating the shooting.

(AP)