You probably did Prob. 12.4 from the point of view of an observer on the ground. Now do it from the point of view of the police car, the outlaws, and the bullet. That is, fill in the gaps in the following table:
$$\begin{array}{|l||c|c|c|c||c|}
\hline \begin{array}{c}
\text { speed of } \rightarrow \\
\text { relative to } \downarrow
\end{array} & \text { Ground } & \text { Police } & \text { Outlaws } & \text { Bullet } & \text { Do they escape? } \\
\hline \text { Ground } & 0 & \frac{1}{2} c & \frac{3}{4} c & & \\
\hline \text { Police } & & & & \frac{1}{3} c & \\
\hline \text { Outlaws } & & & & & \\
\hline \text { Bullet } & & & & & \\
\hline
\end{array}$$