Invisible fences wint stop a dog that wants out. I'm sure this responsible dog owner checked the batteries in the collar first as a test. 
It's apparent by most of these angry comments that's animals have more rights than humans, pretty distorted view. Try to
Negotiate with an aggressive animal and let me know how it goes. These are the same people that bitch about bears and moose in the woods that react with their loose and aggressive animals. 
Easy to judge from a partial recap of the event and form a vile opinion as so many have done here, sorry irresponsible. It just shows that these people place a higher value in a dog than a person.