A section of Interstate 91 in Vermont was closed Monday after Vermont State Police said a U.S. border patrol agent was shot.

COVENTRY, Vt. (TNND) — A U.S. Border Patrol agent shot and killed during a traffic stop in northern Vermont Monday was a veteran of the U.S. Air Force who worked security at the Pentagon during the Sept. 11 attacks, according to his family and officials.

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

The FBI is investigating a Border Patrol agent-involved shooting, according to a statement from the Vermont State Police.

A Customs and Border Protection source has identified the Border Patrol agent shot and killed during a traffic stop Monday as David Maland, 44.

A U.S. Border Patrol agent was fatally shot during a traffic stop near the Canadian border on Monday, according to officials.

An investigation was underway on Tuesday near the United States’ border with Canada, where an agent was fatally shot “in the line of duty,” authorities said

David "Chris" Maland, the U.S. Border Patrol agent allegedly killed by a German national during a traffic stop near the Vermont-Canada border on Monday, was an Air Force veteran.

A U.S. Border Patrol agent killed during a traffic stop near the Canadian border worked security duty at the Pentagon during the time of the Sept. 11 attacks.

He had a tremendous respect and pride for the work he did; he truly embodied service over self,” his family said.

Sources tell WCAX News that a third person may have been involved in the shootout that killed a Border Patrol agent during a traffic stop in Vermont.