"We all thought we could trust her. Never imagined something like this could happen," said the father, identified as "T," in surveillance video footage.
A warning, some viewers may find the video disturbing
The video shows baby monitor footage from a Hillsborough couple's home. The parents, who asked to be identified only by the initials "D" and "T," had just brought their baby girl, "H," home from the hospital in late September.
On the second day, they hired an overnight nanny to help. Weeks later, they say they uncovered something horrific.
"It's definitely horrifying for any parent and family to go through," the father said.
The alleged abuse, they say, was so graphic it cannot be shown on television. In videos, the nanny is seen on multiple nights allegedly striking the baby, shaking her aggressively, and, at one point, throwing her across the room. The child can be heard wailing in distress.
"Just a few days of this kind of abuse could have lifelong consequences for a baby," says Baby H's father.
San Mateo County District Attorney Steve Wagstaffe said his office is working closely with Hillsborough police on the case.
"What struck me overwhelmingly as soon as I read the case was the age of the victim. That's what's so unusual for us," Wagstaffe said.
"If we can convict them, for me, prison is the only answer for someone who would do something such as this repeatedly - not one time in anger or loss of self-control, but repeated," Wagstaffe said. "If the evidence supports it, this person would be going to prison for double-digit years, easily."
KGO-TV is not naming the former nanny or showing her face because she hasn't been charged.
She was hired by "D" and "T" through a social media reference.
"From the phone call we had with her, it sounded very legit, and she seemed like a good nanny," the father said.
"Of course, we interviewed the nanny as well," he added.
The parents say they noticed what they described as aggressive actions weeks into her employment. After firing her, they reviewed the baby monitor footage, which they say revealed the abuse.
Dr. Charles Lorbeer, an expert witness in child abuse cases, says regularly checking baby monitor footage can be critical.
"Some of these cameras will erase themselves in three days, so you've got that little bit of window built in," he said. "It can be as quick as two minutes to fast-forward through. Especially in the initial half hour to an hour, you have to be very deliberate in keeping track of that, especially with someone you don't know."
"Of course we feel guilty as parents," the father said.
After posting a video of the footage on social media, the family received overwhelming support. An online petition calling for accountability has gathered more than 33,000 signatures.
While Baby H has completed an MRI and full body X-ray, her parents continue to monitor her for signs of long-term harm. As difficult as it is, mom and dad are speaking out for a reason.
"My goal is to warn parents about this nanny. I don't want any family, baby or mom to experience this again," says the child's mother.
The San Mateo County DA plans to file charges in the coming weeks.