Rumor and unconfirmed source reporting on other forums suggest the Piper Cherokee variant (either fixed gear PA28 or Arrow, not yet confirmed) entered via midfield crosswind and presumably never saw the Luscombe. The collision apparently occurred as a result of the Cherokee overtaking the Luscombe while either in the turn towards downwind, or as established on downwind. Prop shredded the tail assembly, the loss of control impact therefore inevitable. The Cherokee supposedly flew for a while longer before crashing, others suggest its crash was also immediate with the damage to the prop and airframe.
Condolences to the victims. non-towered airfield ops require a lot of faith on accurate position reporting and vigilance for non-radio players, on the part of all participants. Lack of standardization and differences in equipment, particularly traffic awareness and radios, certainly can contribute to these kinds of accidents. No guarantees in life folks, all we can do is be good stewards in the pattern and practice accurate position reporting. Even with an electrical system one could be in the wrong frequency and not know it, so head on a swivel in an NTA pattern is a must.