GSDs are one of the few breed of dogs who know when they are being abandoned.
I have taken in lots of strays and dump dogs.
I had an elderly friend that had to go to a rest home. She had a GSD that she had since puppyhood and wouldn't agree to go. I agreed to take her buddy so she could get the care she needed.
This is no exaggeration...the poor old pup grieved for 6 months. I feared she might die. The day she finally gave me a half wag of her tail was somewhat of a victory.
Like I said, I've taken in others. Their grief process was sad, but comparatively brief.