Accused Minnesota assassin Vance Boelter's alleged plan to kill more politicians on his target list was foiled by a police sergeant's proactive hunch, and his capture came after he made a big misstep that exposed his whereabouts to an eagle-eyed neighbor, authorities said.

Authorities detained the wife of 57-year-old Vance Boelter, the suspect accused in the deadly shooting of a Minnesota state lawmaker and her husband early Saturday morning.