Over and under watering is one of the quickest ways to kill you bonsai due to the nature of the compromised root system. As winter gets closer, day light hours get shorter, your plant is going to require less and less water. When you bring a plant inside you cut the amount of natural light it gets and therefore cut down on the transpiration rate in the leaves which means your plant will use less and less water. If your leaves (needles) started dropping from the bottom of the plant going up, this is a pretty good sign it was over watered for too long. Top down, under watering. The picture you have posted here does make it seem like the plant is probably dead but do a scratch test on the trunk to see if there is any green inside. If so, there is still some hope. Not a lot mind you but some. Good luck!