The tipster’s call to the local police came in shortly after 9 a.m. Monday from a McDonald’s in western Pennsylvania.

The caller said that a customer there looked like the man in photos shared by New York authorities who were searching for a suspect in the brazen killing of a health insurance executive in Manhattan last week.

When officers arrived at the McDonald’s, on an anonymous, four-lane stretch of road in Altoona, Pa., that is dotted with chain stores and fast-food restaurants, they approached the customer, Luigi Mangione.

“He was sitting there eating,” Joseph E. Kenny, the New York Police Department’s chief of detectives, said at a news conference.

Mr. Mangione was wearing a blue surgical mask and had a laptop, according to a criminal complaint. The officers asked him to pull down the mask.

When he did, one of the officers, the complaint says, immediately recognized him as the man being sought in the killing of the executive, Brian Thompson.