Terrills trespassing on the big Muddy...
Not sure if that was still Julie's ranch or of she had already finalized the sale to McKay.
In any event she authorized the Hannasseys to water their cattle on her land and Jim agreed to it also. For the Terrill clan to come onto her property guns a blazing to drive off Hannassey cattle is a major violation of the mores of that time or any time. They had no right or permission to do that and they were trespassing. She was in her rights to shoot them if she could.
I'm imagining Julie and Jim maintaining 20 well armed cow hands to keep the peace or else both the Terrills and the Hannasseys would be having a war on their property.
Lot's of material for a sequel that is for sure.