Based on the various reports available (Times, BBC, Daily Mail, H&H etc), it does strike me as an accident - not murder. But, perhaps all of the facts are not out in the public domain yet.
There has been suggestions of questionable (low & 'aggressive') flying by this auto-gyro in the past few weeks; and I believe that a report was made to the CAA by the hunt. There has also been a suggestion that the deceased gentleman had gone to the airfield for the purpose of "talking" to the pilot.
I am sure the facts will out, but having lived in Warwickshire all my life, I can safely say that placing your whole hearted belief & trust in Warwickshire Police may result in disappointment. (I can substantiate this with upheld complaints of various natures and IPCC reports into their previous efforts at Major Incident Investigations). Personally, I would attach much more credence to the AAIB report.
Either way, my sincere condolences go out to the family and friends of the deceased chap - whatever happened to "live and let live?".