She did not know why his photograph was taken, but suspected police would use the information if he was ever caught offending in the future.
"This is a form of racism, they're racially profiling our kids," she said.
"The message is, 'we don't trust you. You're gonna f**k up, and when you f**k up, we already have your information and we're gonna get you'."
Indigenous data specialist Karaitiana Taiuru said that was exactly what he believed was happening - that police were using facial recognition technology to profile young, brown faces.
"I suspect those images will be used to either profile Māori youth and to train all their facial recognition AI systems to pick-up Māori and Polynesian faces."
In a response to a request via the Official Information Act, police said its existing NEC facial recognition system enabled them to compare still images of unidentified suspects, where those images had been submitted as part of an investigation.
Police did not say, specifically, whether this facial recognition system was used on images of innocent youths they collected for intelligence and sent to the NIA database.
Amnesty International campaigns director Lisa Woods said she was looking into the issue, and how facial recognition technology could be impinging on young peoples' rights.
"It's a serious issue so it is something we're following and we know that there are issues when it comes to human rights and surveillance that needs to be looked at."
Police said legally photographs of children and young people could be retained if the young person had been arrested or had provided their image voluntarily.
Officers are required to follow an informed consent process for any voluntary photographs, which includes obtaining a signed consent form from the young person and their parent or guardian.
Police can keep the photographs until a parent or caregiver requests that they be destroyed. Parents or caregivers do not need to provide a reason for this.
Many whānau, including the Williams, said their young family members did not give police their consent and the experience left them traumatised.
"I know that he's really distrusting of them now, and that contributed to it. I think he felt targeted because he's brown and I think he felt for his friends," Williams said.
According to a Law Foundation report, published last year, voluntarily provided images from children and young people already exist in a police image management system ABIS 2, which can be searched with facial recognition tools.
ABIS 2 currently holds 1.8 million images from 800,000 individuals.
Taiuru said it was likely Māori would be over-represented in the voluntarily provided images stored there.
"We're already over-represented in the police database for voluntary DNA samples, for example, so this is just another form of police bias and discrimination against Māori."
Police are yet to clarify whether innocent youth photographs collected for intelligence are searchable by facial recognition tools.
Police asked RNZ to provide a privacy waiver in order to comment on Williams' case, but when RNZ provided them with one they said they could not comment while a review into police policy of youth photographs is under way.
