Don't feel a bit of shame in what your did. I live out in the good open spaces of SD. We don't have alot of stray dogs but a few and I am not afraid to say I put around a dozen of them down the past few years. What we really have a problem with is feral cats. Every farm has 10 or more running around. Rule of thumb around here is if its more then a mile from a house without a colar it wasnt let outside to take a dump. Same for a dog. If it shows any sign of being a stray or agressive its going down.If its someones pet that they love so much you think they would atleast colar it and keep track of it. If they don't they didn't care for it that much in the first place...

Don't take it to hard for what you did.