Police and other emergency services eventually arrived at the scene, where Ms Solomona was pronounced dead.
Mr Rae said investigating what happened to the young mother "seems to be quite a puzzle".
"She worked at the freezing works, she liked a drink or two, but there's no indication as to why this actually would have happened," Mr Rae told RNZ.
Ms Solomona worked at Canterbury Meat Packers and had finished an afternoon shift about 1am on Saturday.
She went to a friend's place before ringing her twin sister's partner who agreed to pick her up and drive her to her Cass St home, where she lived with extended family.
Mr Rae said there did not appear to be anyone home, and Ms Solomona's brother-in-law offered to go inside with her.
Ms Solomona said she was fine to go inside alone, and her brother-in-law drove off.
There is a small window between when Ms Solomona arrived home about 2.30am and when her stepbrother found her about 2.45am.
Police said she suffered severe head trauma and a post mortem examination in Christchurch today is expected to reveal more detail about how she died.
Sina lived at the house with her mother Anuella, her mother's partner, her 3-year-old daughter Kaira, her twin sister Loretta, her sister's partner and her two brothers.
None of the family were believed to have been home because they were at another family property in the town.
Anuella Solomona said her daughter was a loving and beautiful person and the family was in deep shock.
"They just don't believe someone could do something like this, if there was any people hate us, any people had trouble, problem with us ... I don't think so," she said.
The family had lived in Ashburton since 2002, with many members working at CMP Canterbury.
Kaira believed her mother was at work and Anuella explained that the only time Sina was not with her daughter was when she was at work.
"She loved her daughter, she loves her friends, she loves anyone. Until now I'm still questioning who would do this," Anuella said.
Mr Rae said police were preparing a time line and looking at CCTV footage from locations in Ashburton.
An unsuccessful search for a weapon on surrounding streets is believed to have been undertaken, and Mr Rae confirmed some items, one of particular interest, was missing from the house and could have been discarded by someone leaving the scene.
Sina did not have a partner, and there was no suggestion she had been drinking after being at work for the evening. She was with friends when she needed a ride home, and got a family member to pick her up.
Police were examining the scene in conjunction with ESR staff and making enquiries to establish her movements in the hours leading up to when her body was found.
"Enquiries have are also being made with her associates and others who may have had relevant information to pass to the investigation. The enquiries are ongoing," Mr Rae said.
He said family members were being helpful.
"They are deeply shocked, they are trying to resolve she's no longer with them."
Sina's body was moved from the house around midday yesterday, and the property was likely to remain cordoned off today as scene examinations continue.
- APNZ and the Ashburton Guardian
