Complex sentence: The James gang had been greatly reduced in numbers by that time; some had fled the gang in fear of prosecution, and many of the original members were either dead or in prison after a botched bank robbery in Northfield, Minnesota.
Split into simpler sentences: The James gang had been greatly reduced in numbers by that time. Some had fled the gang in fear of prosecution, and many of the original members were either dead or in prison after a botched bank robbery in Northfield, Minnesota.