I just do not see LE being able to catch the shooter without serious help from citizens. And in this case, people have to prevent the shooter from being able to get away.
1. wait for a turn or bend in the road
2. ram the blocking vehicle's rear corner which is located on the outer edge of the turn (if the road curves left, then attack the right corner, if the road curves right then attack the left corner.
3. blocking vehicle will enter a 180 degree spin and lose control.