Some hasty explanations. Firstly, this picture is not at all what it appears to be. It's one of those "Perfectly timed pictures" taken accidentally (explanation below). The German Shepherd was my dog, Seeker. He was as bulletproof as any dog I've ever owned. He was gentle as a lamb. He was obedience trained to quite a high level, and showed confidence and poise. This interaction with a young rescue puppy was not haphazard or random. We never allow even a trusted dog with any other animal without close supervision and handling. A 100 pound dog can kill by accident, and I can't tell you how many times I deal with injuries that were not predicted. While no one can claim 100% knowledge of what any animal or person, might do, I can share that Seeker and I knew each other as well as I've known any animal in my career.
Also, it's important to know that this is a picture of a scene that had replayed many times while we fostered the little puppy. Seeker was a father figure, and the little puppy and he would play incessantly. Seeker was so gentle and kind and allowed that little monster to abuse him, without ever a single aggressive response. I caught this "perfectly timed picture" at just the random moment where the pup was tugging on his face and Seeker was pulling away from those little sharp teeth and opened his mouth. It really was like a scene from the Lion King between Mufassa and Simba.
The impression, however, is that this massive dog is ready to end his little playmate, which knowing the reality (which I hope I have outlined sufficiently) couldn't have been further from the truth. But it made for a great picture! Seeker wished he was as tough as this picture made him look, but after being raised with 12 children, 3 cats, a pet duck, a standard poodle who was matriarch of the pack, and a spaniel something or other, he was the low animal on the pecking order... even under the duck. He was one of my best friends and helped us raise many foster dogs during his life, never hurting a single creature.