How old is Sirius? It sounds like he was suffering from a bout of pano - it happens in GSDs when they are growing quickly. My girl went through it several times from 5 thorugh 11 months. It may come back again, Rick, so don't panic - once it happened once or twice for Gracie I didn't even call the vet the latter times! You can search this forum about pano to get additional info. Good luck!!