6UMU531 Confusing exchange at 4 way stop 5/30/2012

Описание: I waited for the car to my left to go through the stop sign and knew I was stopped before 6UMU531, so I started to move after the other car went through the intersection, but 6UMU531 decided to go through as well. Reluctantly gave him my right of way in the confusion. :/

6UMU531 White car