At about 1648 eastern time, a Piper PA-31 suffered a loss of control and crashed at Clearwater Air Park. The pilot-in-command seated in the right front seat and the pilot-rated passenger in the left front seat were killed. A pilot-rated passenger sustained serious injuries. A witness said he saw the airplane on what he thought was final approach to runway 16, but the airplane was very low. The witness reported the airplane made a, sudden, sharp turn to the left. Another witness who was located a quarter-mile from the accident site said the airplane was flying eastbound at a very slow airspeed and banking and yawing left and right. He said it appeared the pilot was executing a go-around, as evidenced by the landing gear retracting, followed by the flaps. The airplane then appeared to make an unstable climb before banking right, stalling and spinning to the ground.