It looks like Basescu wasn’t paying attention to whom he was extending his hand. He was talking with two other apparent admirers while extending his hand in a rather oblivious way. The young teen, judging by the look on the teen’s face, does something inappropriate to Besescu’s extended hand. Without thinking Basescu swats the kid.
Judging by the look on the kid’s face, after he was swatted by Basescu, the kid wasn’t really all that surprised that Basescu reacted that way. The child jumps back, but his face before and after indicates that he had been up to something odd.
I replayed the video and it appears that the child was fondling the tips of Basescu’s extended right hand. Very weird behavior.