On October 17, 2012, about 0800 central daylight time, a Beech model A36 airplane, N121VP, sustained substantial damage when it impacted trees and terrain short of the runway during an instrument approach to runway 12 at the Wausau Downtown Airport (AUW), Wausau, Wisconsin. The pilot received serious injuries. The aircraft was registered to and operated by the pilot under the provisions of 14 Code of Federal Regulations Part 91 as a business flight. Instrument meteorological conditions prevailed for the flight, which operated on an instrument flight rules flight plan. The flight originated from The Waukesha County Airport (UES), Waukesha, Wisconsin, about 0720. The pilot reported that as he neared AUW, the airport automated weather observing system was reporting conditions that were below approach minimums. He stated that he thought the early morning fog would be clearing, decided to attempt the approach, and if necessary perform a missed approach and hold until conditions improved. His written report indicated that he attempted an instrument landing system approach to runway 12. As he descended there was considerable glare reflecting off the tops of the low cloud layer below. Once he had descended into the clouds it became very dark and very turbulent. He stated that his usual practice was to set the decision altitude (DA) and lower the landing gear at the final approach fix. He stated that he believed that he accomplished this on the accident approach. He stated that he did not remember hearing the aural DA warning. He decided to execute a missed approach and began to configure the airplane. He then saw the hills and trees immediately prior to impact. In his written report, the pilot indicated that there were no mechanical malfunctions or failures of the airplane. No mention was made regarding instrumentation failure or anomalies related to the instrumentation or avionics within the airplane.