What’s likely happened?

My papillon, 16 years old in April, when we took him out this morning for his potty break he ended up falling, and was kind of yelping out in pain and shaking. He collapsed, loss consciousness. His tongue turned blue and he stopped breathing, his eyes closed and I couldn’t feel his heart. We thought he had died right there.

My husband went to grab a towel and all of a sudden his leg kicked and he started to breathe really shallowly. We wrapped him up and he kind of freaked out. I’m currently holding him, wrapped in a towel. He’s responding now to my touch on his paws, but at first his legs were just limp. He’s a sleep, kind of snoring. Breaths are shallow but regular.

I know this is a vet emergency, not a Reddit vet emergency. But we are in financial constraints right now, and trying to figure out if this is just his time and we need to make the decision to put him To sleep, or if this sounds like a one off situation, maybe a seizure.. we know he’s lived a long happy life, but making these decisions are so hard.