At 1822 Mountain time, the airplane was destroyed when it departed controlled flight and impacted a highway. Night visual conditions prevailed for the local IFR flight. The Private pilot and sole occupant was fatally injured. Several witnesses in vehicles driving westbound on the highway stated they saw the airplane traveling northwest at approximately 2500 feet agl. One witness stated the airplane suddenly started downward at a steep angle and crashed. Another witness said it took only a few seconds from the time the airplane started downward until it impacted on the highway. A third witness said he saw a green and red light coming down at a high angle and very fast, and he heard [a] loud noise, not [an] explosion. The Roswell Approach Control reported the pilot was cleared to fly the VOR-B approach to the Roswell Industrial Air Center airport. The airplane was on the inbound turn of the procedure turn portion of the approach, heading toward the north. At 1822, Roswell Approach Control lost radar and radio contact with the airplane. At the last recorded radar position, the airplane was approximately 12 nm west of the Chisum Vortac, at 5800 feet mean sea level, and traveling at a speed of 132 knots.