ACT coroner Peter Morrison on Tuesday published his findings on the February 2018 deaths of Anne Wachera Muhoro, 44, her son Ezvin Munene Mugera, 8, and her daughter Furaha Murathime Muhoro, 5.

Mr Morrison ruled the deaths of the young boy and girl, who were both found lying in bed holding a stuffed toy, homicides.

He confirmed his preliminary view that Ezvin and Furaha were already dead when a fire engulfed the family home in Bonner, killing Muhoro, with no other people involved.

The coroner said autopsies had not revealed the cause of either child's death, though forensic pathologist Professor Johan Duflou was unable to exclude possibilities such as suffocation or smothering.

In his findings, Mr Morrison included a detailed outline of Muhoro's activities in the lead-up to the fire, a timeline of her tumultuous relationship with her estranged husband, and evidence from the site of the blaze.

He said the 44-year-old woman's friends had described her as appearing thin, aloof and depressed the month before the fire.

But Muhoro's friends reported noticing "a marked change" in her from about eight days before the blaze, describing her as having become happy, joking, relaxed and more at peace.

"Some remarked that her behaviour was 'out of character' and 'unusually happy'," the coroner wrote.

Her friends said she did not display any of her usual anxiety about upcoming Family Court proceedings, with a custody application made by the children's father listed for the day of the fire.

Muhoro also prepared and signed a will three days prior to the February 19, 2018, blaze, promising each of the children $5000 and appointing guardians for them in the event of her death.

She then took the kids to Kmart Gungahlin and bought a number of toys two days before killing them.

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"Friends and family suggest that Ms Muhoro would usually only buy educational presents for the children and this purchase was out of character for her," Mr Morrison wrote.

Later on the day of the shopping trip, the 44-year-old phoned her mother in Kenya at an inconvenient time and insisted the children speak to their grandmother.

Early on the morning of the blaze, Muhoro used her laptop to remotely access her work computer and erase files before logging into her bank account and paying a number of bills.

CCTV footage captured by cameras from a neighbour's home shows her then fiddling with the fuse box at her house, with Mr Morrison finding she was probably turning off the electricity supply in order to disable the smoke alarm.

A flickering glow at about 4.39am appears to show the start of a fire, with smoke quickly consuming a room in the house.

Firefighters were not called until about four hours later, however, when they received reports of smoke emanating from the property.

They contained the blaze after arriving to find the place well alight.

A subsequent search uncovered the bodies of the mother and her children in the ruins of the house, and what appeared to be torn-up family photos in the bins.

"The evidence points overwhelmingly to a conclusion that Ms Muhoro deliberately lit the fire with the intention of taking her own life and I find that to be the case," Mr Morrison wrote in his findings.

"I am satisfied that both Ezvin and Furaha were killed by their mother in an unknown manner some short time before she lit the fire."

Mr Morrison said the will gave rise to a possible inference that Muhoro had planned at the time of its making to commit suicide, but had only decided later to kill also the children.

He described the children's deaths as "a tragedy" and offered his condolences to their father, who had been denied access to them for several months prior to the fire.

The coroner wrote that there was "no basis for any suspicion" that the father was involved in the killings of his children.

Support is available for those who may be distressed by phoning Lifeline on 13 11 14, Mensline on 1300 789 978, Kids Helpline on 1800 551 800, beyondblue on 1300 224 636, and 1800-RESPECT on 1800 737 732.

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