Eventually, it turned out the swans were killed by a car. At the end of the day, my favorite comment was made by Jim McDonald :
"All the speculation about this incident was disturbing. Bullet wounds, strangling, a psycho killer with a crowbar -- all just made up. Dave Sing made an effort at suggesting that people not rush to judgement. He probably also suspected that a car caused this. I'm sure this isn't the first time he's been called a voice in the wilderness. What happened was that a driver swerved and slaughtered a family of swans. If he had stopped and called the police, how would the result have been better? How will making the driver's name public improve the situation? If the police want to investigate further, fine. I don't think there is a way to determine the speed of the car by how the bones were broken -- as has been suggested -- but if there is, I would hope that technology and the manpower needed to use it would be saved for use on the bodies of human children that are killed by vehicles. Because even though the driver who hit the swans was responsible, the truth is that this was bound to happen. Trumpeter Swans shouldn't have to raise their young on the shoulder of a busy road. They shouldn't have to compete with automobiles for space".
As you might judge on the following picture, taken only 2 weeks before the crash, the Swan were really spending most of their time on the shoulder of the road. I think it is sad, but not too surprising they eventually got hit by a car.
Trumpeter Swan Nest, 2 weeks before the crash