A 69-year-old security guard in Sydney had been fatally injured in brutal attacks by three people who broke into an ice cream kiosk at the Broadway shopping centre around 8:00 pm on Sunday night.

Police said Hanf Schulz, 69, approached two women and a man who were breaking into Wendy's ice cream kiosk. The group had two children in their company.

According to witnesses, a 28-year-old Maroubra woman, a 33-year-old Randwick man and another woman attacked the security guard, when he tried to remove them from the kiosk. The group fled the scene after the bashing.

"(A) female is seen to have punched the security guard in the head," said Acting Inspector Sean Beehag.

"(Another person) punches the same security guard in the head. This blow causes him to drop down to his knees before (a) female is seen to place a frontal kick into the guard's chest causing him to fall to the ground," Mr Beehag said further.

Mr Schultz went into cardiac arrest after the fatal blow to his chest. He died at the Royal Prince Alfred Hospital.

A man and a woman, believed to be a couple, were arrested shortly after the incident. They have been charged with manslaughter. The second woman in the group remains at large.

Police officers are now looking for Raelene from nearby Surry Hills.

The couple's request for bail has been denied. They were to appear in Newtown Local Court Monday.

The couple's children, who were with them at the time of the break-in and arrest, are now under the care of relatives. The children are aged three and five, according to reports.

Highlights:

- A group of two women and a man were seen breaking into Wendy's ice cream kiosk at the Broadway shopping centre Sunday night.

- The group is accompanied by two young children, aged three and five.

- Security guard Hanf Schulz, 69, approached the group and tried to stop the break in. He was attacked violently by the group before they fled the scene.

- A man and a woman were arrested shortly after the incident. The second woman remains at large.

- The couple will appear in Newtown Local Court Monday. They are facing manslaughter charges.

- The children are now with their relatives.