(TNND) — Both state and federal prosecutors have filed charges against Vance Boelter, the man accused of going on a "murderous rampage" that targeted Minnesota state lawmakers.

Acting U.S. Attorney Joseph Thompson said at a press conference Monday that he filed federal murder and stalking charges.

Hennepin County Attorney Mary Moriarty already filed second-degree murder and attempted murder charges, and she told reporters that she planned to seek first-degree charges.

Boelter made his first appearance Monday in federal court, where The Associated Press reported he was appointed a public defender.

Boelter allegedly shot and killed Minnesota state Rep. Melissa Hortman, the Democratic leader and former House speaker.

Hortman’s husband, Mark, was also killed.

Boelter also allegedly shot state Sen. John Hoffman and his wife, Yvette. Hoffman, also a Democrat, and his wife survived the shooting.

“John is enduring many surgeries right now and is closer every hour to being out of the woods,” Yvette Hoffman said in a statement shared by Minnesota Sen. Amy Klobuchar. “He took 9 bullet hits. I took 8 and we are both incredibly lucky to be alive."

Thompson said Boelter visited the homes of two other Minnesota state lawmakers early Saturday, but only the Hortmans and Hoffmans were attacked.

And authorities credited proactive police checks following the first of the shootings with preventing additional deaths.

Thompson said Boelter had guns, a large quantity of ammunition and notebooks listing more than 45 Minnesota state and federal elected officials in his car.

The prosecutor said Boelter planned his attacks carefully, conducting surveillance on the lawmakers’ homes.

Thompson said Boelter’s writings appeared to have been made over the course of months. But he said it was too early to speculate on a motive for the attacks.

“There were some abortion rights supporters, I believe, on the list,” Thompson said in response to a reporter’s question. “But, again, there was dozens and dozens and dozens of names on, you know, hundreds of pages of documents that were recovered with his writings on them.”

Boelter was captured Sunday night after what authorities described as the largest coordinated manhunt in Minnesota's history.

“I want to thank the (Minnesota) Bureau of Criminal Apprehension, the Hennepin County Sheriff's Office, the Brooklyn Park Police Department and the hundreds of local state and federal law enforcement officers who worked tirelessly to apprehend Vance Boelter,” Moriarty said at a news conference Monday. “People were understandably terrified over the last several days, and the state owes you a debt of gratitude for all of your swift work.”

Moriarty said she filed for second-degree murder and attempted murder charges over the weekend against Boelter, before he was captured.

Those were the highest charges they could file by criminal complaint, and Moriarty said they needed to file charges fast to allow law enforcement across the country to arrest the suspect.

Now that Boelter is in custody, Moriarty said they plan to pursue first-degree murder charges.

Craig Trocino, an associate professor of clinical education at the University of Miami law school, said the prosecution needs to show premeditated intent on the part of the suspect to file first-degree murder charges.

And Trocino said that shouldn’t be a problem given the facts of the case.

First-degree murder charges will also need to come through a grand jury indictment, he said.

Trocino said the death penalty is on the table with the federal charges.

He noted that federal prosecutors are charging Boelter with stalking while using interstate facilities, probably because he allegedly used the internet to research his victims.

Thompson, the acting U.S. attorney, said political assassinations are rare.

“But the details of Boelter’s crime are even worse,” Thompson said. “They are truly chilling. It is no exaggeration to say that his crimes are the stuff of nightmares. Boelter stalked his victims like prey. He went to their homes, (impersonated) a police officer, and shot them in cold blood."

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Trocino said the “stakes have risen significantly” after the federal charges were announced.

Trocino called the legal situation “very fluid right now” and expected charges to be changed and added as the investigation unfolds.

“They're filing charges to the extent that they can ... to keep him where he is and get the ball rolling through the prosecution,” Trocino said.

Thompson said Boelter was disguised as a police officer and was wearing a black tactical vest and body armor when he went to the lawmakers’ homes early Saturday.

Thompson said Boelter drove a black SUV with emergency lights turned on and with a license plate that read “police.”

And he said Boelter wore a “hyper-realistic” silicone mask.

Thompson said Boelter’s first stop was the Hoffman residence, and the prosecutor said the attack was captured on a home surveillance camera.

Boelter knocked on the door and repeatedly shouted, "This is the police, open the door,” according to Thompson.

The Hoffmans answered and had a flashlight shined in their faces before they realized the man at their door wasn’t really a cop.

Thompson said Boelter told them it was a robbery and forced his way into their home.

Hoffman fought back, and Boelter shot him repeatedly, according to Thompson.

The Hoffmans’ daughter called 911, which alerted area police and resulted in welfare checks on other state lawmakers.

Thompson said Boelter went to a state representative’s home next, but she wasn’t home.

Thompson said Boelter then went to another state senator’s home and parked in the street in that same black SUV.

A real police officer, around 2:30 in the morning, came by to conduct a wellness check on that lawmaker.

The officer saw Boelter’s SUV parked down the block with the lights on and tried to make contact, but Thompson said Boelter didn’t respond.

So, the officer proceeded to the state senator's home, and she waited for other law enforcement to arrive.

By the time other officers arrived, Thompson said Boelter had left.

Boelter then traveled to Hortman’s home in Brooklyn Park, Thompson said.

He arrived there around 3:30 in the morning in the same SUV made to impersonate a police vehicle, Thompson said.

He parked in the driveway and left the emergency lights on.

Boelter approached Hortman's home, but two Brooklyn Park police officers arrived at the scene before he entered, according to Thompson.

The Brooklyn Park police chief, who spoke at one of the news conferences Monday, credited an off-duty sergeant for being aware of the Hoffman shooting and for telling a couple of his officers to go check on Hortman.

Thompson said that when Boelter saw the officers get out of their car, he drew his weapon and began firing.

Boelter allegedly rushed into the Hortmans’ house through the front door while firing into it.

Thompson said the officers fired at Boelter as he rushed into the home, but Boelter escaped into the home and out the back.

Police recovered the mask, body armor and gun behind the home.

And the police chief said Boelter left behind his SUV with the maps, a list of names and more guns.

Minnesota Bureau of Criminal Apprehension Superintendent Drew Evans said the wellness checks prevented additional attacks that night.

Officials were asked about the number of people on lists found in Boelter’s car and home, and Evans said they were still working through that part of the investigation.

“I do want to continue to clarify, this is not a list of people that was in a numerical order and some sort of ranking,” Evans said. “These are names that are being developed as we are looking at this across multiple writings.”