On October 25, 1996, approximately 1724, eastern daylight time, a Bellanca 8KCAB, N2571Z, was destroyed when it impacted in a river near Sheffield, Massachusetts, while maneuvering after takeoff from the North Canaan Airport, North Canaan, Connecticut. The certificated commercial pilot was seriously injured. Visual meteorological conditions existed and no flight plan was filed for the local flight conducted under 14 CFR Part 91. A pilot had just flown the airplane, and stated that he had no problems with the airplane during his flight. After landing at North Canaan Airport, the airplane was met by a second pilot. The pilots talked and then the second pilot climbed into the airplane. The first pilot stated that he watched the second pilot takeoff in a northerly direction, approximately 1722. He observed the airplane in a left bank, then level off as it went out of his view. Other witnesses stated that they noticed the airplane tip each wing, one after the other, and then the airplane rolled upside down. One witness thought it was going to do a 360 degree roll, but once it got past the 180 degree (inverted) position, it started to descend. The airplane descended gradually at first, then it appeared to go straight down. All witnesses stated that they did not see the airplane impact the ground because of heavy brush and trees obstructing their view. Examination of the wreckage by the Federal Aviation Administration (FAA) Inspector revealed no mechanical problems with the airframe or engine. In a telephone interview with the FAA Inspector, the second pilot stated that he had made a steep bank to the left in order to depart the traffic pattern. Thinking that he caught sight of another airplane in close vicinity, the second pilot made an abrupt turn back to the right. The pilot stated that he felt the airplane shudder, and remembered the airplane being inverted, but could not recall anything after that point. The second pilot thought the airplane had stalled.