OP; Entirely possible that the owner had the dog well attached to the a proper chain and collar, but the dog just worked loose of it. Dogs can sometimes be so smart they can outsmart the best protections, but dumb as a rock when it comes to vehicles and roads.... The worlds dog population is not threatened with extinction.

On the other side, if the owner had been outside the first time the dog chased a vehicle and provided the dog some firm educating, it might still be alive today.

I have heard many folks say that a biker should stop and yell at the dog to stop and get back in his yard... I have done that and it worked about half the time and about half the time I had to defend myself from a snarling beast with pepper spray and a Zephal pump while keeping the bike between us. Screw that. Now-a-days if I can't outrun them or the dog is in front of me, I am glad I keep 2 cans of mace or pepper spray at the ready on the handlebar clip with refills handy in the handlebar bag and the good old Zephal pump is still a friend also and ready to contribute.

/K