Whether to given name or surname is culturally specific. I got suspicious last week when someone I don't know sent me a personal email saying "X and the others

Whether to given name or surname is culturally specific. I got suspicious last week when someone I don't know sent me a personal email saying "X and the others called my employer and got me fired", using the given name instead of surname for person X, like they knew that person. At first I thought it was a veiled threat, but then I realized I was thinking about how I would address that person and that someone else would address them differently.