You need to contact the council and other departments about the dog coming back onto your street after you spoke to the owners. They obviously aren't taking this seriously and you need to keep the relevant authorities informed of any and all instances relating to these dogs.
This needs to be reported and recorded every single time. If this goes south in a bad way, any evidence can be used in court. This includes the dogs wandering unattended into your street days, weeks or months after the original attack. It all adds up in court.
eg: The dogs attacked and killed you dog in December 2020.
You reported it to the Police and council when that happened (have dates, times and whoever you spoke to, get their names and position).
You spoke to the owners about the matter a few weeks later on a particular date. The owners said they would keep it on their property from now on.
The dog has since been into your street on these particular days (at a particular time) and growled, snarled, barked, bared its teeth, whatever, when it saw you and your dogs.
Your dogs were on leads being held by you when this happened.
The offending dog/s was not on a lead and no people were around besides you.
You now carry a large walking stick for protection when out walking your dogs because you fear for theirs and your safety.
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Every time their dog is out in public without a human who can handle and control their dog, it is breaking the law and shows a history of bad animal ownership from the owners.
If the dog is out in public 10 times a month, and its owner is not with it, that shows a clear history of the dog/s wandering at large and the owners doing nothing to control their animals. This type of information can allow the council, animal control or Police to step in and remove the dog/s, or fine the owners, or both.
If you carry a mobile phone when out walking, you can record the dog/s out wandering at large and this adds to the evidence. If you don't have a mobile phone with a camera, get a cheap digital camera and use the video setting to record it. Try to have the time & date setting on the camera if it allows for that.
Basically, you shouldn't have to carry a big stick and yell at an unattended dog in public that has killed one of your dogs and continues to threaten you and your dogs. If it continues to happen, the owners need to be held accountable for their inactions.
Dangerous dogs that have attacked and killed domestic pets, and threatened people, should be put down because they can and do kill people.