The eight-year-old touched a piece of exposed metal, unaware that a faulty wire had made the entire installation live.
Her mother, Rejany Honoria de Almeida, said her daughter was happy the day that she took the pictures and she still cannot come to terms with the fact that a short while later she was electrocuted.
She said: “What was supposed to be a family outing has become a tragedy.”
The parents and their three children had been looking forward to seeing the Christmas decorations at Mestre Orlando Square and arrived around 30 minutes before they were due to be switched on.
The mother said she took the photo of Julia and then let the children run around and play, which was when she touched the live surface and was electrocuted.
She added: “Julia was so happy.
“When the children were playing close to a metal structure that was going to be a tunnel of lights, she put her hand inside and it got stuck there.”
Initially, onlookers managed to resuscitate the girl and she was rushed to hospital, but died shortly afterwards.
The mum added: “My husband picked her up and called the ambulance. She was taken to hospital, but had a massive heart attack.
“She was taken by God.”
The police revealed that council staff had been responsible for setting up the Christmas decorations and were cooperating over the ongoing investigation.
They said that trained workers who had been doing the same job for 10 years were responsible for the entire installation.
The investigation continues.