An F.B.I. agent on Wednesday fatally shot a man in Provo, Utah, who officials said was armed and had threatened to assassinate President Biden just hours before the president was scheduled to speak in nearby Salt Lake City.
Craig D. Robertson, 75, was also charged with threatening to shoot other elected officials, including Alvin L. Bragg, the Manhattan district attorney, as well as with making threats against law enforcement officials, according to court documents filed a day earlier in U.S. District Court in Salt Lake City.
The shooting comes at a moment of intense polarization in American politics. The three indictments of former President Donald J. Trump have offered fodder for supporters and allies, who have seized on his mounting legal peril to fan a narrative of a Justice Department weaponized against him and bent on derailing the Republican front-runner’s campaign to retake the White House.
The F.B.I. said in a statement on Wednesday afternoon that it was investigating an “agent-involved shooting” that had happened around 6:15 a.m. in Provo while agents were trying to serve arrest and search warrants at a home.
A federal law enforcement official, speaking on the condition of anonymity to discuss the shooting, said that Mr. Robertson was armed at the time. Officials offered few other details.
A White House official said that Mr. Biden had been briefed on the matter, and a woman who was listed in public records as Mr. Robertson’s daughter declined to comment when reached by phone.
According to the court filing, Mr. Robertson owned numerous firearms, including a sniper rifle. The complaint also laid out his history of threats on social media, where he referred to his guns as Democratic eradicators. In one post last year, he photographed three rifles and said he was “getting ready for the 2024 election cycle.” He repeatedly taunted the agents investigating him, saying they came close to “violent eradication.”
Last week, he noted on social media that Mr. Biden would be visiting Utah and that he was going to “dust off” an M24 rifle and get out his old camouflage suit, one typically used by snipers.
According to the complaint, other online posts indicated Mr. Robertson’s intent to kill Mr. Biden and Mr. Bragg, who is leading a prosecution of Mr. Trump in New York in connection with a hush money payment to a porn star during his 2016 campaign.
On Sept. 19, 2022, Mr. Robertson wrote on Facebook that “the time is right for a presidential assassination or two.”
“First Joe then Kamala,” he wrote. In another message, he declared that he wanted shoot Mr. Bragg in the head and watch him die.
The post also mentioned George Soros, the financier and Democratic megadonor, who has been a target of Mr. Trump and Republicans in Congress, and echoed Mr. Trump’s attacks on Mr. Bragg and Mr. Soros.
Other subjects of Mr. Robertson’s threats: Attorney General Merrick B. Garland, whom he described as a Nazi; Gov. Gavin Newsom of California; and Letitia James, the New York attorney general.
In September 2022, referring to Ms. James, Mr. Robertson wrote on Facebook that “a sniper’s bullet does not recognize your qualified immunity.” In October 2022, he shared a picture of a semiautomatic handgun, calling it a “Merrick Garland eradication tool.”
In yet another Facebook post in October, Mr. Robertson described a “patriotic dream” in which he said stood over a wounded Mr. Newsom, “my suppressed S&W M&P 9mm still smoking.”
In a Facebook post in March, Mr. Robertson taunted the F.B.I.
“To my friends in the Federal Bureau of Idiots: I know you’re reading this,” he wrote.
Spokespeople for Mr. Bragg and Ms. James declined to comment.
The F.B.I. has been increasingly concerned about threats to its agents. Last year, law enforcement officers shot and killed a man who they said tried to break into the F.B.I.’s Cincinnati office.
And a Tennessee man accused of assaulting the police during the Jan. 6 attack on the Capitol faced additional charges of plotting to assassinate several of the federal agents who had investigated him. He was also accused of planning an attack on the F.B.I.’s field office in Knoxville, Tenn.
Mr. Trump and his supporters have downplayed the notion that his incendiary criticisms of the Justice Department and the F.B.I. are anything other than an expression of legitimate grievances.
But federal and local authorities have remained on heightened alert, providing additional security to prosecutors investigating Mr. Trump and the judges presiding over his cases.
Zolan Kanno-Youngs and Jonah E. Bromwich contributed reporting. Kitty Bennett contributed research.