Complex sentence: Brooks found no evidence of direct involvement by Brigham Young, but charged him with obstructing the investigation and for provoking the attack through his rhetoric, until recently many considered her book the definitive work on the massacre.
Split into simpler sentences: Brooks found no evidence of direct involvement by Brigham Young, but charged him with obstructing the investigation and for provoking the attack through his rhetoric. Until recently many considered her book the definitive work on the massacre.