The mother of a murdered nine-month-old believed another woman was caring for her daughter, only to find out her partner had thrown their baby into the Tweed River, New South Wales police will allege.

Court documents revealed the family of four had been sheltering from a storm in a Tweed Heads shopping centre about 6.30pm on Saturday.

CCTV footage shows the family walking through the shopping mall, their children wearing only nappies and the nine-month-old riding in a shopping trolley.

The family huddled in a rear car park when the father took the baby, telling his partner he was going to give the child to another woman.

While the mother waited with their two-year-old son, police will allege the man walked to the water’s edge and tossed the infant into the river.

He then returned to his family before the trio caught a bus to the Gold Coast.

The girl’s body drifted more than 30km in the ocean current before washing ashore on Surfers Paradise beach.

At 12.26am on Monday, police were called to a domestic incident in a Broadbeach park where the girl’s father was arrested, and eight minutes later, her body was discovered on the beach.

The documents also detailed the final hours of the baby’s life on Saturday.

It is alleged Queensland police were called to the family at Broadbeach about 3am, finding the man and woman highly intoxicated.

“Concerns were held for their ability to provide care and shelter for their children,” the documents state.

The family were taken to a home at Kingscliff, where neighbours said they heard a baby cry about 3.30am and a man knocking on a door asking to be let in.

The family stayed at the apartment until catching a bus for Tweed Heads about midday, police will allege.

The family allegedly spent the afternoon near the Jack Evans Boat Harbour when the father asked another woman to take their baby.

The man allegedly told the girl’s mother: “Let them have this time to themselves to get to know each other.”

But a short time later the woman allegedly handed the girl back, saying: “I can’t do it, I’m living on the street.”

Locals have since left flowers, teddy bears and written notes at Tweed Heads, where she was allegedly killed, and at the site where she was found at Surfers Paradise.

Mourners gathered at the beach at sunset on Thursday to pay their respects and encourage the community to step in and help people in need.

Organisers of the memorial asked the community to direct their support towards charities that help children in need.

“It was really just trying to direct everyone’s generosity to the right support services and charities available,” organiser Lauren Paris told the Seven Network.

The father was charged with murder on Thursday and appeared in Tweed Heads local court where his matter was adjourned to 25 February.