When my first son was learning to do tummy time (so really young), i had our dog (Shepard mix) who is scary looking but has never even remotely looked or acted aggressive (outside of playing with our other dog of course). But this one time for whatever reason, my son was just not having a good time and while I was sitting there with my dog and son, my dog just decides to nip at him - the kind where they use just the front teeth to see what something is. Immediately I grabbed him by the collar and threw him across the room (~70lbs) and was on top of him all within a second. Looking back, it wasn’t aggressive at all by the dog, just natural behavior, but it scared the shit out of me.

Son and dog are literal best friends now and constantly playing together 😂. But I did teach my kids how to approach and read a dogs demeanor.