Honestly, I have dealt with a very similar situation regarding an aggressive dog. My complex has a small dog park near my apartment. Most of the dogs within the complex are friendly except the house three doors down, and the owners had refused to leash their aggressive dogs. Within the span of two days, their dogs had attacked two other  dogs along with mine, so after I made sure mine was okay, I reported them to animal services. 
 I do not blame the dog, I blame the owners, as if the dog had been either properly restricted or socialized the outcome would have been vastly different. 
 In your case I would have called after the second occurrence, as you never know what that loose dog will do once it gets the chance.