I've seen and heard plenty of stories of guinea pigs killed by dogs, too - and three of them were family piggies of ours, not thanks to a neighbours' dog working its way through their badly maintained fence and breaking into what we thought was a safe, lidded run in an enclosed garden while we were at school!
It only takes seconds to bite; you cannot step in that quickly.
I have also seen too many frightened piggies in those videos and photos that are shared online; the signs are usually subtle, but they are there.
Excitable dogs and guinea pigs do not mix. Dogs are still predators with a predator's instinct. Guinea pigs are prey animals, first and foremost. They are not animated dog toys, as tempting as the idea is. Please keep them apart!