The piston twin was destroyed following a loss of control during its initial takeoff climb from the Harry P. Williams Memorial Airport (PTN), near Patterson, La., at 0954 Central time. The ATP-rated pilot and his dog were fatally injured. Visual conditions prevailed for the planned flight to the Houma-Terrebone Airport (HUM), near Houma, La. One witness observed the airplane climbing at a steep nose-high attitude with the gear and flaps retracted. At approximately 800 feet agl and approximately halfway down the runway, the witness observed the airplane start a slow left turn and reported that both propellers were turning. The witness said the airplanes initial turn was slow, but then developed into a rapid and tight turn continuing until the airplane was in the inverted position. Once inverted, the airplanes nose dropped and the witness reported seeing the entire under- and topside of the airplane as it made approximately two rotations before impacting the ground adjacent to the runway on private property.