Thompson was shot in the back by a masked gunman when he arrived at a hotel for an investors' meeting with his company.
Police tracked Mangione five days later to a McDonald's in Altoona, Pennsylvania, during the nationwide search.
He was found with a ghost gun, fake ID, passport, and a handwritten document detailing his "motivation and mindset."
Thompson's murder had triggered debate on the US healthcare system's operation and treatment by insurance firms.