The killings of a Border Patrol agent in Vermont last week, a state’s witness in California, and a pair of senior citizens in Pennsylvania all appear to be linked to a fringe group of West Coast vegan activists and artificial intelligence theorists.

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.

The woman accused of shooting and killing a U.S. Border Patrol agent will remain behind bars.Teresa Youngblut allegedly shot and killed David “Chris” Maland during a traffic stop on Jan. 20 on Interstate 91 in the town of Coventry not far from the Canadian border.