The man charged with killing one Minnesota politician and wounding another visited the homes of other Democrats on his alleged hit list, according to prosecutors.
Along with attacks on the homes of Democratic state politicians Melissa Hortman and John Hoffman, Vance Boelter is accused of stalking the homes of two other legislators on the night of the shootings.
One of those state representatives was on vacation and the suspect left the other house after police arrived early on Saturday, acting US Attorney Joseph Thompson said.
Ms Hortman and her husband Mark were killed in the attacks while Senator Hoffman and his wife Yvette were wounded in a shooting at their home.
Mr Boelter carried out surveillance missions, took notes on the homes and people he targeted and disguised himself as a police officer just before the shootings, Mr Thompson said.
"It is no exaggeration to say that his crimes are the stuff of nightmares," he said.
Mr Boelter surrendered to police on Sunday night after they found him in the woods near his home following a massive search that stretched over two days.
Investigators say Vance Boelter appeared to have spent months preparing for the shootings — the latest in a string of political attacks across the US.
Federal prosecutors charged Mr Boelter, 57, with murder and stalking, which could result in a death sentence if he is convicted.
He already faces state charges, including murder and attempted murder.
At a federal court hearing on Monday in St Paul, Mr Boelter said he could not afford an attorney. A federal public defender was appointed to represent him, and he was being held without bail pending a court appearance next week.
Manny Atwal, his lead attorney, declined to comment, saying the office just got the case.
Notebooks allegedly show careful planning
Mr Boelter had many notebooks full of plans, Mr Thompson said.
Underscoring what law enforcement officials said was the premeditated nature of the attacks, one notebook contained a list of internet-based people search engines, according to court records.
But authorities had not found any writings that would "clearly identify what motivated him," Mr Thompson said.
Though the targets were Democrats and elected officials, Mr Thompson said it was too soon to speculate on any sort of political ideology.
All of the politicians named in his writing were Democrats, including more than 45 state and federal officials in Minnesota, Mr Thompson said.
Elected leaders in other Midwest states said they, too, were mentioned in his writings.
Authorities declined to reveal the names of the other two politicians whose homes were targeted but escaped harm.
Democratic senator Ann Rest said she was told the suspect parked near her home early on Saturday. She said in a statement that the "quick action" of law enforcement officers saved her life.
Mr Boelter sent a text to a family group chat after the shootings that said: "Dad went to war last night … I don't wanna say more because I don't wanna implicate anybody," according to an FBI affidavit.
His wife got another text that said: "Words are not gonna explain how sorry I am for this situation … there's gonna be some people coming to the house armed and trigger-happy and I don't want you guys around," the affidavit said.
Police later found his wife in a car with her children. Officers found two handguns, about $10,000 in cash and passports for the wife and her children, according to the affidavit.
Suspect caught in woods near his home
Just hours after the shootings on Saturday, Mr Boelter bought an electronic bike and a Buick sedan from someone he met at a bus stop in Minneapolis, the federal affidavit said.
Police found the sedan abandoned on a highway Sunday morning.
In the car, officers found a cowboy hat Mr Boelter had been seen wearing in surveillance footage as well as a letter written to the FBI, authorities said.
The letter said it was written by "Dr Vance Luther Boulter" and said he was "the shooter at large".
The car was found in rural Sibley County, where Mr Boelter owned a home. A police officer later saw Mr Boelter running into the woods.
He was found within 20 minutes — 1.6 kilometres from the home — and gave himself up, crawling out before he was handcuffed and taken into custody in a field, authorities said.
Coordinated attacks on legislators
Drew Evans, superintendent of the state Bureau of Criminal Apprehension, said the rampage likely would have continued had Brooklyn Park officers not checked on Ms Hortman's home, causing Mr Boelter to flee.
The Hoffmans were attacked first at their home in Champlin. Their adult daughter called 911 to say a masked person had come to the door and shot her parents.
Mr Boelter had shown up carrying a flashlight and a 9 mm handgun and wearing a black tactical vest and a "hyper-realistic" silicone mask, Mr Thompson said.
He first knocked and shouted: "This is police," according to prosecutors.
At one point, the Hoffmans realised he was wearing a mask and Mr Boelter told them: "This is a robbery."
After Senator Hoffman tried to push Mr Boelter out the door, Mr Boelter shot him repeatedly and then shot his wife, the prosecutor said.
A statement released on Sunday by Yvette Hoffman said her husband underwent several surgeries.
"He took 9 bullet hits. I took 8 and we are both incredibly lucky to be alive," the statement said.
When police in nearby Brooklyn Park learned that a politician had been shot, they sent patrol officers to check on the Hortmans' home.
According to the affidavit, Brooklyn Park police officers arrived just in time to see Mr Boelter shoot Mark Hortman through the open door of the home.
They exchanged gunfire with the shooter, who fled into the home before escaping.
Ms Hortman was found dead inside, according to the document. Their dog also was shot and had to be euthanased.
Search for motive continues
Writings recovered from the fake police vehicle included the names of politicians and community leaders, along with abortion rights advocates and information about healthcare facilities, said two law enforcement officials who spoke to The Associated Press on condition of anonymity because they were not authorised to discuss details of the ongoing investigation.
Friends and former colleagues interviewed by the AP describe Mr Boelter as a devout Christian who attended an evangelical church and went to campaign rallies for US President Donald Trump.
Mr Boelter is also a former political appointee who served on the same state workforce development board as Senator Hoffman, records show, though it is not clear if or how well they knew each other.
AP/ABC
