Lets try this one on for size. What if the original story is the Adams/Landrew verison that Roger likes. Reason we can't find records of the first massacre was because NM wasn't part of the US.

Then the second Adams is the first Adams son who starts to try and rediscover dad's gold. Then comes Davidson, Brewer and the rest of the gang.

Same place/same location/same name just different time frames.