Our German shepherd attacked our Staffordshire Terrier. What steps can we take to stop this from happening again?

As the title reads, that pretty much explains it. They’re both females and both spayed. This fight was brutal, my husband was the only one in the yard and it took at least 5 minutes to break it up by the time I came outside. Our German shepherd wanted to kill our other dog, there was blood everywhere and they weren’t stopping even while trying to break it up. Our GS was latched onto our other dogs neck while the ST was latched onto our GS torso and legs.

They have never fought before and I’m just at a loss because it happened randomly in the yard. The GS came at the our other dog who was pooping at the time, she did not like it and growled but by that point within 10 seconds the fight had started. They do not have any toys, food or other resources in the yard. Our GS seemed to have pushed the other’s boundaries and did not like her response.

How do we stop this from happening again? We immediately separated them and assessed the wounds on both dogs. Our Staffordshire terrier had to go to the veterinary clinic & Our German shepherd was okay for the most part.

They don’t really interact with eachother much to begin with, they typically do their own thing and stay out of each other’s way. They do not share food bowls and they do not eat together either. I’m just looking for all advice! I hope their relationship can recover from that fight and that this isn’t a repeated issue.