Federal agents are investigating after a US Border Patrol agent was shot and killed Monday afternoon on the highway in Vermont.

A U.S. Border Patrol agent was fatally shot Monday on a highway in northern Vermont south of the Canadian border, authorities said. The death was confirmed by the FBI and Benjamine Huffman, acting secretary of the Department of Homeland Security in Washington.

Officials said the agent was shot “in the line of duty” on Interstate 91, which was closed for several hours near the border with Canada.