\begin{tikzpicture}[scale=1.2,
  vect/.style={->,shorten >=3pt,>=latex'}]
   \tkzDefPoint(2,1){A}
   \tkzDefPoint(6,2){B}
   \tkzDefPointWith[orthogonal,K=.5](A,B)
   \tkzGetPoint{C}
   \tkzDefPointWith[colinear=at C,K=.5](A,B)
   \tkzGetPoint{D}
   \tkzMarkRightAngle[fill=gray!20](B,A,C)
   \tkzDrawSegments[vect](A,B A,C C,D)
   \tkzDrawPoints(A,...,D)
\end{tikzpicture}
