The weapon that killed Agent David Maland last week in northern Vermont was bought by a person of interest in a double murder two years ago in Delaware County, state police say.

As the sprawling investigation unfolds, here’s an overview of the key figures involved and their alleged connections.

New details regarding the fatal shooting of Minnesota-born U.S. Border Patrol agent David Maland have been revealed in court. The 44-year-old was fatally shot while conducting a traffic stop in Vermont on Jan. 20. He was from the Blue Earth area and graduated from Fairmont High School.