In reply to Ethan.

Ethan, thank you for your feedback. Of course, you can combine this circles-drawing functionality with multiple markers.

To delete a circle you will need to call the setMap method on the Circle object with null as an argument:
mycircle.setMap(null);

You can probably implement this using double click (dblclick) as an event for the circle deletion. That is you will create a circle by clicking on Google map, and you will delete the circle by double clicking on the circle. See this Google Maps API Events Handling.