Battery exhausted on Nikon Coolpix S9100?

Hi! I have a relatively new Nikon Coolpix S9100. One day, while plugged in and charging, the green light on top started flashing. When I turned on the camera, I got a “battery exhausted” message and the camera would not operate. Any idea what I did and what happened? Is the battery shot? How can I avoid doing this in the future?

Thanks! -M