Despite prominent signs showing that leashes are required, there are probably more unleashed dogs per mile of the Eagle Creek Trail than on any other Columbia River Gorge trail. The media didn't say if this particular dog was leashed or not. With a leash, at least you can keep the dog away from the edge!
After the last time I was on this trail (two years ago), I refuse to take my dog on it any more. Having an unleashed friendly dog come up to greet my leashed dog resulted in the leash wrapped around my legs several times, a bit scary in such surroundings. Then later that same day my dog was bitten by a dog belonging to some idiot who never bothered to control their dog and didn't bother to apologize, either. Fortunately it wasn't serious. But I'm off that trail for good. Too bad, because it's definitely the most scenic of all the Gorge trails. It's also one of the most crowded after Multnomah Falls.
BTW, that trail is wider than it looks in the photo! Note also the cables to hold onto for those who are acrophobic.
Suggested way to hike the Eagle Creek trail: start at the crack of dawn, and hike maybe a mile above Twister Falls (the falls just above the more famous Tunnel Falls), which is where the mobs turn around. Time how long it took you to get there. Take a good book and a sleeping mat. Spend the day reading and sleeping. Time your departure to get back to the trailhead just before dark. You'll be ahead of most of the crowds going up and behind them coming back.
As a variant, backpack the Eagle Creek trail to Wahtum Lake, again leaving at the crack of dawn. Return via the PCT and Ruckel Creek trails, which are delightfully uncrowded.
Oh, and hope that your car hasn't been broken into; the trailhead parking lot is the worst for car-clouting in the whole Gorge. The Forest Service recommends parking down the road at the fish hatchery or close to the campground host. In any case, leave nothing (of value or otherwise) in your car.