The shattered parents of the baby girl who apparently died outside a Sydney childcare centre after being left inside a hot car have spoken out about their devastating loss.

Baby Olivia Ancelet was found dead strapped in her car seat outside the Earlwood centre on Tuesday afternoon, having been left in the vehicle for “an extended period of time on a very hot day”, police said.

She was reportedly discovered when her father, Etienne Ancelet, arrived about 5.30pm to collect her from the centre in Sydney’s inner-west – only to be told by childcare staff that she had not been dropped off.

Ancelet then reportedly ran outside to find the little girl, who celebrated her first birthday in December, strapped into her booster capsule.

“I’ve killed my daughter,” he screamed, according to witnesses, as he made the horrific discovery.

Local resident Ray Gomes was alerted by Ancelet’s screams.

“All the neighbours were really good, putting water on her [and] trying to cool her down, because she was obviously still very hot,” he said.

Olivia was pulled from the car and given CPR by neighbours and passers-by. NSW Ambulance paramedics arrived but could not save her. She was declared deceased at the scene.

Baby Olivia’s parents have spoken out after the tragedy. Photo: Facebook

On Wednesday, Ancelet and Olivia’s mother, Kim Visconti, spoke out about their grief.

“Olivia was a sweet and beautiful baby, who was the light of our lives,” they told news.com.au.

“We are humbled and grateful for the time we had her. We are devastated by what has unfolded.”

The couple said they wouldn’t wish such an incident on any other parents.

“We will always cherish our time with our beautiful girl. She was loved by all that knew her,” they said.

“It is an unimaginable time of sorrow for us.”

Ancelet had changed his Facebook profile picture to a black screen by Wednesday afternoon. Little Olivia was reportedly his and Visconti’s only child.

Temperatures in Sydney rose into the 30s on Tuesday amid a NSW heatwave warning.

Police established a crime scene and took both parents for questioning. They have also spoken to workers at the childcare centre.

Ancelet was later taken to hospital suffering from shock. He is reportedly yet to give police a formal statement.

Superintendent Christine McDonald said baby Olivia’s death was “an absolute tragedy”.

“The information provided to us suggests that this baby was left inside the vehicle for an extended period of time on a very hot day,” she said at the scene.

“Leaving a child in a vehicle at any time can be dangerous.

“Leaving a child inside a vehicle for an extended period of time can be deadly.

“This is an absolute tragedy — the death of a one-year-old baby girl.”

McDonald said her thoughts were with all those involved and impacted by the “deeply traumatic” incident.

“This has a rippling effect right throughout our community because so many of us can put ourselves in a similar situation.”

The couple said they were working with police as the investigation into the tragedy continues.