Convicted murderer Chris Watts had just strangled his wife Shanann to death when his eldest daughter Bella wandered into the room.
The four-year-old girl asked an innocent question - most likely the last words she ever uttered.
'What are you doing with mummy?' she asked.
The chilling details of Watts' heinous plan to murder his wife and two daughters Bella and Celeste have been revealed during a tell-all interview on Dr Phil with Shanann Watt's family attorney.
After murdering his wife and unborn child, Watts reportedly turned his attention to his two girls.
'He walks over and takes Cece's favourite blanket and smothers her. At that point, Bella says: "Please, daddy, do not do to me what you just did to Cece",' lawyer Steven Lambert said.
'And then he killed Bella.'
After strangling his wife with his bare hands and suffocating his two little girls, Watts dumped their bodies in an oil field.
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Watts initially denied any involvement in his wife and daughters' disappearance, even appearing on a local news station to plead for their return.
Lambert said Watts was wrapping his wife's body in a sheet when Bella walked in.
'She's four, what we've been told she's quite smart - was quite smart - and knew something likely was up,' he told Dr. Phil.
'And what he said was that, "Mommy is sick, we need to take her to the hospital to make her better".'
Watts pleaded guilty to the murders in November last year and was sentenced to life behind bars.