The phrase is, "I acted to protect myself" applies here. No need to get bitten or mauled by dogs that are improperly trained. The owner will have to learn from this. I can understand your guilt in taking a life though, sometime's it doesn't satisfy to hear "It wasn't your fault." It's tough to think about what you could've done, but my own safety comes before others'.

If it was me, I would tell the owners what happened and ride away without even giving my name. Not much more than that though. I'm afraid of my fellow Americans trying to sue me for any little issue, even if I feel can win the court case.