The man suspected of stabbing his two-month-old granddaughter to death in Brisbane's south remains under police guard in hospital but is unlikely to be questioned for several days.
Qianqian "Queenie" Xu died in hospital on Wednesday, shortly after police swooped on a Parkinson home and found the baby, her mother Yuanyuan Cao and grandparents all seriously injured with knife wounds.
Qianqian's father, Ms Cao's husband George, only discovered the horror after arriving home from work to be told by police.
"He initially wasn't advised about his daughter until he took it up with detectives," Detective Inspector Tony Duncan said on Thursday.
"He spent most of the afternoon with his wife after they were advised that his daughter had passed away.
"As you can imagine they are very traumatised over the whole incident. It was a horrific crime scene."
The girl's grandfather, a Chinese national, is under police guard at Princess Alexandra Hospital but police will only consider laying charges once they have spoken to the 53-year-old.
They say it could be several days before that happens, as they wait for doctors to give the all clear.
"From the information we have it indicates that the grandfather may have been responsible," Det Insp Duncan said after stressing the investigation was ongoing.
Detectives, unaware of a motive, are also looking at whether mental health issues may have played a role.
Asked if the alleged attack seemed to come out of the blue, Det Insp Duncan replied: "Yes".
"The father actually expressed his surprise that anything had happened," he said, adding that there was no history of violence at the house.
"But to date we are just trying to identify what the motivation was for this offence."
Ms Cao's parents arrived from China last month to help care for their granddaughter and neighbours have described the family as normal and quiet.
Det Insp Duncan said police were called to the house about 2.30pm on Wednesday after Ms Cao fled to a nearby house to raise the alarm.
The grandfather, soaked in blood, was arrested on the driveway of the family property soon after.
Inside the house, officers found Qianqian lying in a bassinette with stab wounds, while her grandmother was lying on the floor seriously injured.
Police and paramedics tried desperately to save the girl but she died a short time later in hospital.
The grandparents underwent major surgery on Wednesday night and remain in critical but stable conditions.
Ms Cao also suffered defensive stab wounds but was expected to be released from hospital as early as Thursday evening.
In a Facebook post last year she wrote: "15/10/15,3:28am, my little princess was born 3.1 kg at mater hospital" before posting a photo of Queenie.
The stabbings have deeply upset residents in the quiet middle-class neighbourhood.
A woman who lives near the house said she was absolutely devastated and in shock.
"You just never imagine something like this can happen," the neighbour told AAP.
"They were just normal, quiet people. You would see them in the park or walking around."
*National domestic violence helpline: 1800 737 732 or 1800RESPECT. In an emergency, call triple zero.
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