Dog behave differently in different situations.
Sometimes with their "owners" but the owner is not the alpha, they will exhibit signs of aggressiveness more so in a protective manner. Same deal with property, property the see as their territory make them feel the need to be "on guard".
Also most dogs are aggressive to other dogs, not so much with people other than the mailman.
Were you wearing a matching kit?
I don't think these dogs were vicious but they most definitely show signs of aggression.