Luigi Mangione admitted Friday to fatally shooting UnitedHealthcare CEO Brian Thompson as he pleaded guilty to two federal stalking charges, marking a major development in the high-profile case.

During his appearance in federal court, Mangione acknowledged planning and carrying out the shooting of Thompson in Manhattan.

Mangione told the court that after years of experiencing severe pain from a back injury, he learned UnitedHealthcare was holding its annual investor conference in New York City.

He said he contacted the company while posing as an investor with more than $50 billion in capital to obtain the precise location of the conference.

Mangione also admitted preparing a firearm before traveling to New York.

“Before traveling to New York, I used a 3-D printer to make part of a gun, and I equipped the gun with the silencer and the magazine,” he told the court.

Mangione said his trip to New York and his communication with UnitedHealthcare were undertaken with the intention of shooting Thompson.

“I shot Mr. Thompson in Manhattan and he died,” Mangione said, adding that he knew his actions were illegal.

Thompson’s family issued a rare public statement following the guilty plea, describing the development as an “important step toward justice.”

Meanwhile, Mangione’s attorneys filed a motion seeking dismissal of the separate charges he faces in New York state court, arguing that continuing the prosecution would violate the state’s double-jeopardy protections.

The federal guilty plea represents a significant turn in a case that has drawn widespread national attention since Thompson’s killing.