When the parents of 7-month-old Finn Jordan hired Alexis Khan, they thought they had found a decent babysitter. Apparently not, all thanks to their loyal hero family dog which acted as the baby's protector every time he was left to the care of the 22-year-old young woman.

Benjamin and Hope Jordan of Charleston, South Carolina hired Ms Khan immediately after having moved into their new neighbourhood in 2012. They said they did a background check on the young woman, who had already held previous babysitting jobs, and she came off clean.

"We felt like Alexis was a good fit at the time," Mr Jordan said.

However, way into her fifth month of employment, the Jordans noticed something peculiar with their family dog, Killian, every time Ms Khan would come in to report for work for the day.

Dog Killian and Baby Finn Jordan

"About five months into her being our baby sitter, we started to notice that our dog was very protective of our son when she would come in the door," Mr Jordan told WCSC. "He was very aggressive towards her and a few times we actually had to physically restrain our dog from going towards her."

They said they found it unusual that Killian was behaving in such a manner towards since he had been a quiet and friendly dog.

The Jordans discussed the matter and agreed to do some home-style investigation of their own. Upon Mrs Jordan's suggestion, they hid an iPhone under the couch, left it just turned on in the hopes to capture anything not good that happens in their household while go off to work, leaving the three at home.

Court documents stated they said they expected to hear her abusing the dog to explain Killian's aggression towards her. What they found out shocked them both. They heard slapping and lots of crying, definitely not from Killian, but from Finn.

"It started with cussing," Mr Jordan said. "Then you hear slap noises and his crying changes from a distress cry to a pain cry. I just wanted to reach through the audio tape, go back in time and just grab him up."

"To know that five months I had handed my child to a monster, not knowing what was going on in my house for that day," baby Finn's father added.

They even heard her say "shut the f*** up" and hurled expletives towards the 7-month-old.

"We just could not believe it," Mr Jordan said. He said they immediately took Finn to the hospital to have him checked out for any possible physical injury. Thankfully, the doctors ruled the baby boy is in perfect shape and in the pink of health.

A few weeks after the incident, Charleston City Police arrested Ms Kahn. She confessed guilty to the crimes of assault and battery.

She had been slapped to a maximum three years imprisonment. Her name will also be listed in a registry of child abusers, preventing her from having the chance to work again with children.