It’s actually very likely the guy didn’t even have a knife. I had a mentally ill guy once approach me and my friend while we were hanging around in the street waiting for the store to open. He was rambling a bit but he mentioned he was gonna get hit shotgun and kill someone (he didn’t specify us, in fact I don’t think he ever made a direct threat against us, but it was clear he was trying to scare us). My friend was sweating bullets but I just asked if he was hungry and gave him my bag of trail mix. He left, confused. I’m quite sure he didn’t have a shotgun.

People are so used to violent confrontation in the United States that just suggesting violence indirectly can be enough to scare them into giving you something. Anon’s “mugger” was probably doing this.