Boelter allegedly shot dead Melissa Hortman, the top Democrat in the Minnesota House, and her husband, Mark, in their home on Saturday - a crime Governor Tim Walz characterised as a "politically-motivated assassination."
Authorities said Boelter also allegedly shot and wounded another Democrat, state Senator John Hoffman, and his wife Yvette at their home a few miles away.
"After a two-day manhunt, two sleepless nights, law enforcement have apprehended Vance Boelter," Walz told a news conference on Sunday.
"One man's unthinkable actions have altered the state of Minnesota.
"A moment in this country where we watch violence erupt, this cannot be the norm. 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, and each and every one of us can do it."
Walz said Hoffman, who had been hit with nine bullets, came out of his final surgery and was moving towards recovery.
Officials earlier said the gunman had left behind a different vehicle outside Hortman's house in suburban Minneapolis that resembled a police SUV, including flashing lights, and contained a target list of other politicians and institutions.
Boelter has links to evangelical ministries and claimed to be a security expert with experience in the Gaza Strip and Africa, according to online postings and public records reviewed by Reuters.
Boelter was charged with two counts of second-degree murder and two counts of second-degree attempted murder, a Hennepin County criminal complaint showed.
Three of those charges are punishable with jail terms of up to 40 years, according to the complaint unsealed on Sunday.
Boelter fled on foot early on Saturday when officers confronted him at Hortman's Brooklyn Park home, said authorities who had warned residents to stay indoors for their own safety and unleashed the state's biggest manhunt.
When police searched Boelter's SUV after the shootings they discovered three AK-47 assault rifles, a 9-mm handgun, and a list of other public officials including their addresses, the criminal complaint showed.
Working on a tip that Boelter was near his home in the city of Green Isle, more than 20 SWAT teams combed the area, aided by surveillance aircraft, officials said. Boelter was armed but surrendered with no shots fired.
The killing was the latest episode of high-profile US political violence.
Such incidents range from a 2022 attack on former Democratic US House Speaker Nancy Pelosi's husband at their home, to an assassination bid on Donald Trump last year, and an arson attack at Pennsylvania Governor Josh Shapiro's house in April.
