The questions everyone's asking about the horrific murder of a mother and her little girl.

It is the mystery that has gripped the entire nation.

A woman’s remains found in New South Wales’ Belanglo Forest – the country’s most notorious dumping ground – in 2010.

The remains of a little girl discovered in a suitcase discarded off a South Australian Highway earlier this year.

The victims of both seemingly unrelated cases remained unidentified until just yesterday, when police announced the devastating discovery that the duo were actually mother and daughter.

But as more facts about the horrific double murder emerge, more and more questions are being raised.

How can a mother and daughter just disappear?

Police say Karlie Jade Pearce-Stevenson, 20, packed up her life in Alice Springs and left with her daughter, two-year-old Khandalyce Kiara Pearce, to travel and find work between 2006 and 2008.

They were last seen on November 8 that year, driving on the Stuart Highway near Coober Pedy.

Police say the pair’s movements after that are relatively unknown, but that they travelled through central Australia, Adelaide and probably Victoria and Canberra.

Why did no one report them missing?

Karlie’s mum, Khandalyce’s grandma, filed a missing person’s report in the Northern Territory in September 2009.

But police say she withdrew the report six days later after being reassured by someone that “Karlie was safe and well, but did not want family contact at that time”. Her family believed the duo were living interstate.

A former family friend told News Limited Karlie struggled after have Khandalyce. “After the baby, things went downhill. Unfortunately things happen with families,” he said.

So why was no one looking for them?

Police were told Karlie, a single mother, was occasionally in contact with her mother, but the contact became less frequent.

Karlie’s mother died in 2010 – the same year the body of her daughter (who was not identified until recently) was discovered in Belanglo Forest.

A Facebook group called ‘Help Find Karlie’, started to find her when her mother was ailing, was taken down a month ago.

How did the bodies of Khandalyce and her mother Karlie end up 1100km away from each other?

Police believe Karlie’s body may have been dumped in the notorious forest to deliberately throw investigators off the scent. The Belanglo State Forest was the well-known dumping ground of backpack murderer Ivan Milat. Karlie’s body was found close to where Milat’s victims were discovered.

South Australian Police were unwilling to speculate about where the pair were actually murdered, saying they were not yet 100 per cent certain so did not want to release incorrect information into the public domain.

Currently, the whereabouts of Karlie and Khandalyce before they were killed and the location of the crime is not known.

How did police finally link the bodies?

Publicity surrounding the discovery of Karlie’s remains in the Belanglo Forest included a fairly accurate computer-generated image of her face and description of her clothing (which led to the nickname “Angel” due to her top, which had the word ‘angelic’ on it), but led to no clues about her identity.

In July this year, the Khandalyce’s bones were discovered in a suitcase of dumped by a South Australian highway, just outside the small town of Wynarka. Clothes and a quilt located with the remains provided no answers for police

Seven years since the last known sighting of the pair, they received a breakthrough tip-off on October 8 – the 1267^th Crime Stoppers call regarding the case. The caller suggested Khandalyce may have been the victim. Another witness provided photos of Khandalyce with the quilt found in the suitcase. Another had seen the pair at an Adelaide shopping centre in November 2008 and took a photo of the young girl in a pink dress identical to the one found with her remains.

Police obtained a blood sample from Khandalyce’s medical records, which matched the remains in the suitcase. Knowing the description of the girl’s mother roughly matched that of ‘Angel’, police compared DNA profiles to discover the forest remains were those of Karlie.

Police say the lives of both mother and daughter met extremely violent ends.

What’s the story with Khandalyce’s father?

Karlie was a single mum. Her ex-boyfriend, Khandalyce’s father, still lives in Alice Springs and has been ruled out as a suspect in the violent crimes by police. So have Karlie’s stepfather and stepbrother.

The family have released a statement saying they are devastated by the news and trying to deal with the grief.

So who did it?

Police have a main suspect in the case after being inundated with information and tip-offs over the past 24 hours, Fairfax Media reports.

The male suspect is reportedly serving a sentence in a NSW jail for unrelated offences. Police said they were still “keeping an open mind” and following a number of leads in the case.

Milat, his killer nephew, Khandalyce’s father and Karlie’s family members were earlier ruled out as suspects.

How could someone violently kill a young mum and little girl?

This is the question that will likely never have an adequate answer.