Who are you?

Two days ago, something weird happened. I went out for dinner. While walking back to our car after dinner, we pass another eatery. Some of the eatery's tables were set on the five foot way. I was walking without paying much attention to the surrounding. Then out of nowhere, while I walking, suddenly there was a hand in my face. I was kind of stunned. Thought it was a friend of mine, so I turned to look at the owner of the hand. Then that freaky guy grinned and wave at me. My look says "Who are you? I don't know you."