A random act of...littering?

A very strange thing happened to me in San Francisco.  Sara and I were headed down the escalator into the underground to catch the metro.  A youngish, lanky, red-headed fellow was on his way up and passing us as we went down.  Suddenly, out of nowhere, he whips a cardboard box at me.  It was some sort of empty food container, and it hit me squarely in the chest.

My immediate reaction was to whip around and stare at him, but already he was above me and I was lookng at the back of his head.  "WELL THAT WAS UNUSUAL!!" was all I thought to yell.  What I felt like doing was running back up the escalator and sucker punching him in the back of his head.  But I am not stupid, and resisted the urge to start a physical fight with a strange man on the street of a strange city.

Sara missed the incident, as she was in front of me on the down escalator.  When I told her what happened, she mused..."He was probably on drugs."

Clearly he was taking the wrong drugs.  Or perhaps he wasn't taking the right ones.

Dear box-man, I am only wondering...why me?  Was it coincidence?  Or did something about my appearance make you so angry you had to whip something at me?