Thats a healthy looking Coyote.

BIL had one run up his yard and snatch a chicken right at his feet. His singular PET chicken of all things. So he goes running after it but alas,coyote won.

Another group spent months setting up a smaller dog of mine,Woofer.He thought he was tough but in reality it was he wasnt too bright. They managed to study his habits for months and one night they got him,never to be seen again. His sister,however,never ventured more than 3 feet (seriously) from my Black German line male GSD,she died a natural death.A group of coyotes had no interest on taking on the GSD at all.

So to answer the question,yes,your dog was at risk IMO.An ambush is indeed what you may have seen,I know Woofer did.