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.

Teresa Youngblut, 21, faces federal firearms charges in the Jan. 20 death of Agent David Maland. She’s accused of opening fire on agents during a traffic stop in northern Vermont, sparking a shootout that also left her companion, Felix Bauckholt, dead.