Attorney Brett Branham told WSOC he was at work when a contractor upstairs saw the act.
He said the driver never turned around to get the puppy.
After seeing that the dog had road rash and a broken back leg, Branham called Ark Animal Hospital for help.
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But that wasn't all he did. He also posted a video to his Facebook page asking for help finding the dog's owner.
"You couldn't think of anything better to do than throw this dog out of your moving vehicle going 45 miles per hour?" Branham said in the video. "We're calling the cops. It's just so sad. He's got a broken leg now, we'll take of him but help us find out whoever did this."
Branham's video has been shared more than 26,000 times.
"If you commit to do something like care for a life, it deserves to be treated with dignity and respect," said Branham.
The puppy, deemed Good Sam by Ark Animal Hospital, is now recovering.
A GoFundMe page has been created to help pay for her veterinary bills.