The airplane experienced an in-flight loss of control and crashed into a wooded area at about 1045 Central time. Instrument conditions prevailed. The airplane was destroyed by impact and a postcrash fire; the commercial pilot and two passengers died. The flight proceeded normally to the destination airport and, at approximately 1033, the pilot contacted the tower. After some vectoring and communications difficulty, a pause was noted and then grunting sounds were recorded on the frequency. The controller asked the pilot if he needed help and he responded, “I got it into a spin and I cant stop it.” Heavy breathing/grunting sounds were heard on the frequency. At 1044, the controller advised the pilot to climb immediately to 3000 feet. The pilot responded with unintelligible words.