Vance Boelter, 57, has been charged in the shootings of two Minnesota lawmakers and their spouses. The Hennepin County Attorney said Monday that her office intends to pursue first-degree murder charges against him as well.

Authorities arrested and charged Vance Boelter on Sunday night after he allegedly shot and killed House Democratic leader Melissa Hortman and her husband in their Brooklyn Park home and shot and seriously injured state Sen. John Hoffman and his wife in their home in Champlin.

Vance Boelter has been formally charged in the shootings of two Minnesota lawmakers and their spouses, with the FBI revealing that he visited the homes of several other elected officials on the same night he fatally shot State Rep. Melissa Hortman and her husband, and separately wounded State Sen. John Hoffman and his wife.

Surveillance footage captured an attempted murder, according to charges unsealed Sunday: A man wearing a mask, a blue shirt and police-style tactical vest with a badge knocked on a door in Champlin and announced himself as a police officer. He then entered the house and shot Minnesota Sen. John Hoffman and his wife.

The Hennepin County Attorney’s Office unsealed the criminal complaint charging Vance Boelter with two counts of second-degree murder and two counts of second-degree attempted murder.

Federal prosecutors revealed in a six-count complaint that Vance Boelter has been charged with murder, stalking, and firearms violations. The Acting U.S. Attorney for the District of Minnesota, Joe Thompson, said on Monday during a press conference that “It is no exaggeration to say that his crimes are the stuff of nightmares.”