[grania]

It's really awful when something like this happens. I'm a dog owner and I used to be an avid bike rider, so I get the dilemma. For a bike rider, a dog coming up and getting tangled in a bike wheel is as dangerous as one that bites. This dog could easily have been set off if there was something about the bike rider that brought back the war experience.

It sounds like wrong place, wrong time for both the dog and the bicyclist. FWIW, in a case like that, (after once tumbling over the handlebars due to a dog) I used to get off the bike and get past the dog.

[Altariel]

I wonder if it was the sound of wheels on a road coupled with a helmet.

Given the dog’s background, he may equate “helmet” with “soldier” and decided that he needed to protect his master from an unknown “soldier”