From Fox News:
Rookie Altoona police officer Tyler Frye took Mangione into custody after an employee and a customer at a McDonald’s in the town thought he looked like the suspect on a wanted poster and called authorities.
When officers approached Mangione, who was wearing a mask and a beanie and working on a laptop in the back of the restaurant, and asked him to remove his face covering, they recognized him as the suspect wanted for questioning in Thompson’s murder.