At 0724 local time, the twin turboprop destroyed when it impacted trees and terrain in Ferndale, Md., while approaching Baltimore-Washington International Airport. The solo ATP flying the non-scheduled cargo flight under FAR Part 135 was fatally injured. Visual conditions prevailed for the IFR flight from Philadelphia. At 0721, with the flight about 10 nm northeast of the airport, the pilot was cleared to land. Radar returns show the airplane continued on a westerly track, north of the airport, bypassing the approach end of Runway 33R consistent with a modified downwind for Runway 15L, and descended to 700 feet. Just prior to the Runway 15L abeam position, the airplane began a left turn. One witness noticed the airplane flying very low near a high school. It all of a sudden made a very sharp bank to the left, then began tilting right, then left, and finally back to left over a 180-degree bank, and directly into the ground. All flight control surfaces were accounted for at the scene, the landing gear and flaps were up and both engines exhibited signatures consistent with power being produced at the time of impact.