So, it ended up that the ostriches that were running around on a SeaTac road were not ostriches, but they were pet emus instead. In fact, the story first reported by the media had some errors.
First, they were emus. Second, two birds died. Third, it may be that the dog actually didn’t kill the birds directly. The father emu died of a heart attack and one of the poor youngsters died after running into a fence.
The dogs, suspected to be Great Pyrenees (seriously?), are still on the loose and animal control officers are still on the lookout for the culprits. In other cities, they have wild dogs that kill rabbits. In the Seattle-area, you have big fluffy purebreds that kill exotic flightless birds.