The man accused of assassinating Minnesota House Speaker Emerita Melissa Hortman and her husband, and shooting a state senator and his wife, had also targeted two other Minnesota lawmakers early Saturday morning.
Boelter now faces several federal and state charges as laid out by prosecutors on Monday.
Acting U.S. Attorney Joe Thompson says Vance Boelter went to the homes of a Maple Grove state representative and a New Hope state senator before killing the Hortmans in their Brooklyn Park home.
Thompson says he planned his attacks carefully.
"He researched his his victims and their families. He used the internet and other tools to find their addresses and names, the names of the family members," says Thompson. "He conducted surveillance of their homes and took notes about the location of their homes."
Hennepin County attorney Mary Moriarty says they're pusrusing first-degree murder charges against Boelter.
"I want to assure our community and all those who are grieving that we will seek justice and accountability for the victims of all these heinous crimes," says Moriarty. "Our most senior and experienced prosecutors are handling this case."
With charges coming from the feds - who say their case will litigated first but will not eliminate any of the state charges - there are questions about how the two prosecutions would work together. Twin Cities defense attorney Mike Bryant explained to WCCO Radio how it's likely to unfold.
"Sometimes the feds let the state continue to do what they're doing, and then they just do something if they need to, or if they wanna add charges after," Bryant said. 'Sometimes they just come in and take over."
This appears to be a case where the feds are going to take precedent but if there's no agreement between the federal government and Moriarty's case? What happens at that point might be unknown according to former Hennepin County Attorney Mike Freeman, who says he can't think of a single case over the last several decades where an agreement wasn't reached on who would prosecute the case first.
Freeman says the major difference could come down to whether or not the U.S. Attorney's Office will seek the death penalty.
"The principal difference between what the feds can do and state can do, as I see in a case like this, is a death penalty," Freeman told WCCO's Chad Hartman. "Minnesota has considered the death penalty on a number of occasions. The legislature and the people have said no."
If Moriarty and Thompson can't come together on how to proceed, Freeman said it's unclear who has final say in the matter.
"I don't know what happens here, because it's kind of unprecedented," Freeman explains. "Now, I'm certain that it's occurred elsewhere, but normally one or the other stands down and lets the other go forward. And as I said, usually the determination is who has the strongest, who the facts of the case, what are the facts of the case that leads to the most likelihood of successful prosecution."
Freeman says the question of whether or not to pursue the death penalty is not cut-and-dry however. If convicted, there's no chance - based on a first-degree murder charge - Boelter would ever get out of prison.
"The only difference between that is whether someone is put in the electric chair or injected lethal drugs," says Freeman. That's really the only question here. And I think that question, in my view, that question ought to be decided by the people of Minnesota. We have done that numerous times in the Minnesota legislature, which is refused to adopt the death penalty."
However, at least at this early stage, Thompson says they can't determine what sentencing they'll pursue in the case.
Monday afternoon, Boelter made his first federal court appearance in St. Paul where he's being held by federal marshals. Boelter will make an appearance in Minnesota state court "virtually" on Monday.
The court has ordered Boelter remain in custody and his next hearing is scheduled for June 27. Boelter has stated he cannot afford an attorney and for now he will appoint a federal defender pending an inquiry.