Complex sentence: After several Union organizers were killed and narrowly escaping death, he retreated to woods where It possessed him, leading him to slaughter several anti-union organizers, possibly involved in the murder of his comrades, in broad daylight at the Silver Dollar Bar.
Split into simpler sentences: After several Union organizers were killed and narrowly escaping death, he retreated to woods where It possessed him. This leads him to slaughter several anti-union organizers that were possibly involved in the murder of his comrades, in broad daylight at the Silver Dollar Bar.