Minnesota Governor Tim Walz said 57-year-old Vance Luther Boelter was arrested on Sunday.
A massive manhunt for 57-year-old Vance Luther Boelter had been underway following the shooting deaths on Saturday of Melissa Hortman, the top Democrat in the Minnesota House, and her husband, Mark, which Walz characterised as a "politically motivated assassination".
"One man's unthinkable actions have altered the state of Minnesota", Walz said as he paid tribute to his colleague and friend Hortman, saying she "was the core of who our values were".
"This cannot be the norm," he told reporters.
"It cannot be the way that we deal with our political differences. Now is the time for us to recommit to the core values of this country."
Authorities said Boetler also shot and wounded another Democratic lawmaker, state Senator John Hoffman, and his wife Yvette at their home a few kilometres away.
Boetler was charged with two counts of second-degree murder and two counts of second-degree attempted murder, according to a Hennepin County criminal complaint.
Walz said Hoffman came out of his final surgery and was moving towards recovery.