\begin{tikzpicture}[->,>=stealth,shorten >=1pt,auto,scale=0.6, transform shape]
% x node set with absolute coordinates
\node[state] (A) at (0,0) {$A$};
\node[dstate] (B) at (0,-1.5) {$B$};
\node[dstate] (C) at (-1,-3) {$C$};
\node[state] (D) at (1,-3) {$D$};
\node[state] (E) at (0,-4.5) {$E$};

% Directed edge
\path (A) edge (B);
\path (B) edge (C);
\path (B) edge (D);
\path (C) edge (D);
\path (C) edge (E);

% Bidirected edge
%\path[bidirected] (A) edge[bend left=60] (C);
\end{tikzpicture}
