Bergen was given medical care until his owner was found, and then he was transferred to an animal hospital. He died overnight.
Investigators learned that Bergen's owner had left the dog indoors when she went to work on Wednesday, but a man was to care for him while she was gone, Nelson said. Investigators have tried to contact that man, who is suspected of leaving Bergen on the balcony, but he has not replied.
Absent any further contact, investigators plan to forward an animal cruelty case against him to prosecutors, Nelson said Thursday afternoon.
The Humane Society of Utah called for felony charges of animal torture.
"There must be justice for Bergen," said Gene Baierschmidt, executive director of the society. "A message must be sent to our community that this type of treatment of animals simply will not be tolerated."
Bergen is one of two dogs to die in two days due to heat and dehydration.
A Rhodesian ridgeback died Tuesday afternoon during a hike near Red Butte Canyon, at the "Living Room" overlook, Nelson said.
The dog was one of two hiking with a man who was caring for them while their owner was out of town. They had hiked for about two miles in an hour while temperatures reached 95, when the dogs began to struggle, said Salt Lake City fire department spokesman Jasen Asay.
Another hiker called for help while the dogs were given water, but when crews arrived one of the dogs had died. The other was unresponsive when rescuers arrived and was wheeled down the mountain on a stretcher. The surviving dog has recovered, Nelson said.
"If it's too hot for you, it's too hot for them — and they're wearing the fur coat, so their temperature can rise very quickly," Nelson said.
She urged residents to watch for any pets suffering in hot temperatures and report them to Animal Services at 801-743-7045.
"It takes a community," Nelson said. "If you notice something looks amiss with an animal, call us. We have to give kudos to [Bergen's] neighbor for stepping up and saying, 'Something is not right here.'"