Trajectory depends on the gun.   These were just handguns.   Many handguns shoot anything but flat.

And the 100 yards between them was heavily forested.   There is no way that they could have seen her through 100 yards of woods.  Go take a look at the terrain on Google Maps.

I would bet anything that it was probably Field's girlfriend, and not himself, that fired the errant rounds.   Shooting a handgun accurately is a very difficult skill to learn.   Very few women are proficient in shooting handguns.  I wonder if he may have even been trying to teach her how to shoot.

Still, the shooting took place on Field's property.   And I would bet that both handguns probably belonged to him too.   So he would clearly have primary responsibility for any accident taking place.