ordered it had he known about it.

Rather, my argument is twofold:

1) An Apostle was there in the days prior to the massacre and spent days and multiple meetings discussing what to do. I consider it very unlikely that a group of hyper-religious people would have directly disobeyed an Apostle's orders/counsel days after he left. So at absolute best, the counsel left open the possibility of killing everyone.

2) Overall Climate - Keep in mind that the Old West was a violent place. Vigilante justice was common. Utah was, in some ways better and in some ways worse. There was generally less lawlessness in Utah, but there was certainly a climate of religious zealotry in Utah in the 1850s and 1860s that led to multiple instances of violence toward apostates, 'sinners', Indians, non-Mormon settlers etc. Go read some BY, Jedediah Grant, or Heber C Kimball speeches from this time. It's red hot rhetoric. Violence was in the air. This isn't even debatable in my estimation.