(GREEN ISLE, Minn.) -- The man suspected of shooting and killing a Minnesota lawmaker and her husband as well as shooting and wounding a second lawmaker and his wife "stalked his victims like prey" and "shot them in cold blood," acting U.S. Attorney for the District of Minnesota Joseph Thompson said.
"His crimes are the stuff of nightmares," Thompson said at a news conference as he outlined the "chilling" details.
Vance Boelter, 57, is accused of killing Democratic Minnesota state Rep. Melissa Hortman and her husband, Mark, and wounding Democratic state Sen. John Hoffman and his wife, Yvette, in "political assassinations," Thompson said. Boelter allegedly showed up to their doors in the middle of the night impersonating a police officer and wearing a realistic-looking mask, officials said, noting that two other lawmakers were spared the night of the shootings.
Boelter, who was arrested overnight near his farm in Green Isle, Minnesota, is facing federal charges including stalking and firearms charges and state charges including first-degree murder, officials said.
Boelter allegedly had firearms and a list of 45 elected officials in notebooks in his car, Thompson said.
He allegedly surveilled his victims' homes and took notes, Thompson said. In a search of a home in north Minneapolis tied to Boelter, authorities seized a list of public officials that had a notation under Melissa Hortman's name reading, "married Mark 2 children 11th term," according to the affidavit. Another notebook included an added notation next to Melissa Hortman's name reading, "Big house off golf course 2 ways in to watch from one spot," the affidavit said.
Thompson outlined the four homes that Boelter allegedly drove to early Saturday.
Boelter allegedly first drove to Hoffman's home in Champlin, Minnesota, in a black SUV with emergency lights turned on and a license plate that said "police," Thompson said.
Hoffman's "chilling" security camera footage showed the suspect in a black tactical vest, body armor and a "hyper-realistic silicon mask," Thompson said. Armed with a flashlight and a 9 mm Beretta handgun, Boelter allegedly knocked on the front door and repeatedly shouted, "This is the police, open the door!" Thompson said.
When Sen. Hoffman and his wife came to the door, the suspect shined the flashlight in their faces, said there was a shooting reported in the house and asked if the couple had weapons, Thompson said.
The Hoffmans shouted, "You're not a cop!" Thompson said, and then the suspect announced that "this is a robbery" and he forced his way into the home.
When Sen. Hoffman tried to push the suspect out of the house, Boelter shot him and his wife, Thompson said.
The Hoffmans' daughter called 911, Thompson said.
At 2:24 a.m., Boelter allegedly drove to a state representative's house in Maple Grove, Thompson said. That lawmaker was not home as she and her family were on vacation, Thompson said, and Boelter left the scene.
Boelter then allegedly drove to a state senator's home in New Hope and parked on the street, Thompson said.
At 2:36 a.m., after learning of the shooting at Hoffman's home, New Hope police dispatched an officer to the New Hope lawmaker's house, Thompson said. When the officer arrived, she saw Boelter's car parked down the block and she believed Boelter was an officer dispatched to the scene, Thompson said.
The officer pulled up next to Boelter, rolled down her window and tried to speak with him, but he did not respond and stared straight ahead, Thompson said. So the New Hope officer drove to the state senator's home and waited for other law enforcement, and by that time, Boelter had left the scene, Thompson said.
State Sen. Ann Rest identified herself as that lawmaker who was spared.
"I am so grateful for the heroic work of the New Hope Police Department and its officers. Their quick action saved my life," she said in a statement Monday. "I am also thankful for the work of state and local law enforcement to apprehend the suspect before he could take any more lives."
Rest added, "I grieve for the loss of Melissa Hortman and her husband Mark, and I am praying for the recovery of John and Yvette Hoffman."
After the Hoffmans were shot, officers also proactively went to the home of his fellow lawmaker, former Speaker of the Minnesota House of Representatives Melissa Hortman, in the nearby town of Brooklyn Park.
When two Brooklyn Park officers arrived, they saw Boelter's SUV in the driveway with emergency lights flashing and Boelter standing in front of the house a few feet from the door, Thompson said.
When Boelter saw the officers, he allegedly started firing and rushed into the house, killing Hortman and her husband, Thompson said.
The Brooklyn Park officers fired at Boelter while he allegedly rushed into the home, but Boelter escaped into the house and out the back, Thompson said.
The officers who confronted the suspect likely prevented other shootings, according to Drew Evans, superintendent of the Minnesota Bureau of Criminal Apprehension.
The target list recovered from the suspect's car outside the Hortmans' house had a list of dozens of Minnesota Democrats, including Hoffman, Hortman, Gov. Tim Walz, U.S. Rep. Ilhan Omar and U.S. Sen. Tina Smith, according to law enforcement sources familiar with the matter.
The shootings sparked a massive, two-day manhunt that included 20 SWAT teams, helicopters and unmanned aerial vehicles, authorities said.
Boelter was armed when he was apprehended in a rural area late Sunday, authorities said, but he was taken into custody without incident.
Boelter, who is in federal custody, made a brief first appearance in federal court on Monday, wearing a two-piece orange jail suit, orange socks and black slides. Boelter said he has about $20,000 to $30,000 in his bank accounts and asked for a public defender. His combined preliminary and detention hearing was set for June 27.
A motive is unclear, Thompson said.
According to an interview with an unnamed witness, Boelter tried to buy an electronic bike and a Buick in north Minneapolis at 7 a.m. following the attacks, and allegedly drove with the witness to a bank where he withdrew $2,200 in cash, according to court documents.
Hours after the shootings, Boelter allegedly texted his family, "Dad went to war last night ... I don't wanna say more because I don't want to implicate anybody," according to the affidavit.
Boelter also allegedly texted his wife, "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."
In a search of Boelter's wife's car, law enforcement recovered two handguns, approximately $10,000 in cash and passports for Boelter's wife and her children, the affidavit said.
ABC News' Pierre Thomas, Katherine Faulders, Mike Levine, Alexander Mallin and Brittany Shepherd contributed to this report.