Luigi Mangione Pleads Guilty to Stalking, Confesses to Killing Brian Thompson

Luigi Mangione just pled guilty to stalking in his federal case in the killing of UnitedHealthcare CEO Brian Thompson ... a stunning move that could torpedo his upcoming New York state murder trial.

Mangione spoke to the judge, saying ... "After years of enduring pain from a broken back, I shot Mr. Thompson, and he died. I knew what I was doing was illegal." His lawyer, Karen Friedman Agnifilo, said during a news conference, "He endured years of severe, debilitating pain, following a broken back, while struggling to navigate our health care and health insurance systems," adding, "He believed that the system had failed him and destroyed his life."

Agnifilo is previewing what she will argue before the judge when it comes time for sentencing ... that Luigi was so overwrought with pain and anger he was not fully in his right mind when he fired the shots that killed Brian Thompson.

Mangione said he tracked Thompson to a UnitedHealthCare conference, where he posed as an investor to get more info on who was attending. He said he used a gun he printed on a 3-D printer and affixed it with a silencer.

Mangione pled guilty to interstate stalking resulting in death and stalking through the use of interstate facilities resulting in death.

Thompson's family was in court to watch the dramatic turn of events. Afterward, the family said they are happy Mangione has been held accountable for "this heinous act," adding, "Now we look to the court to ensure that sentencing reflects the severity of this crime."

The plea in Manhattan federal court will bring an abrupt end to a case that had been headed for trial in January ... and just a month before he is scheduled to stand trial in New York state court on murder and other charges.

The plea comes after sources with direct knowledge told TMZ Mangione's lawyers were in serious negotiations with federal prosecutors over a deal involving a possible guilty plea.

That would allow Mangione's lawyers to present mitigating factors -- including his feelings about healthcare and corporate greed, and how they allegedly affected his mental state -- in hopes of securing a sentence more favorable than life in prison.

The judge said there was no plea agreement ... meaning Luigi did not cut a deal with the government before today's hearing. Instead, he pled to the 2 charges against him, and is essentially throwing himself at the mercy of the judge, hoping for less than a life sentence.

In fact, the judge acknowledged Luigi received a letter from the government stating the sentencing guidelines provide in the general range of 24 to 30 years. The judge has a lot of discretion in sentencing. The judge said Mangione would serve at least 85 percent of his sentence. If he is sentenced to 24 years, that would mean Mangione would serve a little over 20 years, at least.

Before Mangione is sentenced, the judge will receive a pre-sentencing report about all things Luigi. There will also likely be a hearing where the defense can present evidence of Mangione's mental state at the time of the killing. The federal judge, Margaret Garnett, a former New York U.S. Attorney, is well-respected and considered tough.

The federal plea could have major consequences for Mangione's upcoming state case. We're told lawyers will argue New York can no longer prosecute him over the same killing because that would constitute double jeopardy. Mangione's lawyers filed legal docs today in state court, asking the judge to dismiss the case on grounds of double jeopardy.

Even if the state case survives that challenge ... Mangione's lawyers could pursue an extreme emotional disturbance defense without worrying about how it might affect the federal case.

Mangione previously pleaded not guilty to second-degree murder and weapons charges in his New York case ... his state trial is scheduled to begin September 8.

The Manhattan D.A.'s office issued a statement after the plea in Mangione's federal case, saying ... "Since December 2024, the Manhattan D.A.'s Office has been tirelessly preparing to pursue a trial conviction in New York State Supreme Court for the alleged cold-blooded murder of Brian Thompson. We are encouraged that Mr. Thompson's family received a measure of accountability today. While federal sentencing is pending, we are prepared to litigate the defense motions. The Manhattan D.A.'s Office remains committed to seeking justice for Mr. Thompson and his family."