It's not a crime to hate. In America, anyone can believe in the most toxic, radical ideas, as long as they don’t act upon them.

What might have pushed Luigi Mangione over that line has emerged as the pressing question in the aftermath of his arrest in the assassination-style shooting of UnitedHealthcare CEO Brian Thompson, a man who never saw it coming on a sidewalk in Manhattan.

Mr. Mangione, 26, was arrested Monday in Altoona, Pa., 280 miles west of New York City. He is charged with second-degree murder and is being held at SCI-Huntingdon until he is turned over to New York authorities.... [snip]

Mr. Mangione is a University of Pennsylvania graduate and a member of a prominent real estate family in Maryland. Investigators are looking into an accident that injured Mr. Mangione's back and sent him to an emergency room in July 2023. They say his writings about the injury and his criticism of corporate America and the U.S. health care system could be tied to the shooting of Mr. Thompson, 50, on Dec. 4. ... [snip]

Mr. Mangione could also face domestic terrorism charges — similar to those filed against an 18-year-old man who pleaded guilty to fatally shooting 10 Black people at a Buffalo, N.Y., supermarket in 2022.

Few states have had as long a history of domestic extremism — or as violent a recent past — as Pennsylvania. Now, the state finds itself in the spotlight of another incident, leaving residents grappling with the aftermath.