I’m so sorry this happened
A couple of things from the paddock pictures - as endlessclimb said, the gate was likely not installed properly. Secondly, that area where a sort of chute is created beside the barn - that is an accident waiting to happen again. If the BO does nothing else, that little funnel should be removed by continuing the horizontal fence along to the barn at the other end and having the gate installed there.
Anywhere you have a funnel sort of zone you have a danger zone and an area that’s more likely to get broken leading to loose livestock.