Police have arrested Luigi Mangione, a 26-year-old software engineer, in connection with the fatal shooting of UnitedHealthcare CEO Brian Thompson. Mangione, of Maryland, was arrested Monday morning at a McDonald’s in Altoona, Pennsylvania.

Mangione was taken into custody on local firearms charges, New York Police Commissioner Jessica Tisch told reporters. He has not been charged in connection with the shooting but is believed to be “the person of our interest,” Tisch said.

Police were led to Mangione through a “combination of old-school detective work and new technology,” Tisch said.

Despite little visible evidence, a McDonald’s employee recognized Mangione on Monday morning and called police New York Times Reports. “He just sat there and ate,” NYPD Chief Detective Joseph Kenny said at a news conference Monday.

Mangione reportedly had a gun, a silencer and four fake IDs. The gun appeared to be a 3D printed “ghost gun,” Kenny told reporters. After his arrest, Mangione showed police a fake New Jersey ID, Kenny said. The ID was the same one used to check into a Manhattan hostel on November 24, eight days before the shooting. Sources also say this New York Post that he brought with him a “manifesto” criticizing the US healthcare industry.