The operator reported that the pilot was on an instrument flight rules (IFR) flight plan and was on a return flight to an airport after retrieving a company airplane. Radar data revealed that while on the approach path to land, about 3 miles from the destination airport, the airplane descended to 25 ft above the ground and shortly thereafter, the airplane impacted powerlines and came to rest on a rooftop. The airplane sustained substantial damage to both wings, the fuselage, and empennage. A local law enforcement officer reported that as the pilot was being transported to the hospital, he stated that he was disoriented during the approach. The officer added that the visibility during the time of the accident was less than ¼ of a mile. The operator reported that the pilot did not inform him or the other company pilot flying ahead of him in another airplane of any mechanical malfunctions or failures to the airplane or engine that would have precluded normal operation prior to or during the flight.