Killer Chris Watts is suffering in prison as he is 'tormented' by his sick crimes.
The evil father murdered his family on August 13 last year - dumping daughters Bella, four, and Celeste, three, in oil tankers.
He also slaughtered his 15-weeks pregnant wife Shanann, 34, before dumping her body in a shallow grave at the oil site in Colorado.
Watts, 34, was sentenced to five life sentences and jailed at a maximum-security prison in Wisconsin.
Now, a source has said Watts is suffering his own "private hell" after finally taking responsibility for his heinous crimes.
The source said: "He thinks about what he did every day.
"He is tormented by his past and the mistakes he made.
"He said he has finally taken responsibility for his actions. He has nothing to do but think."
Last month it emerged Watts had told a prison guard how evil spirits made his slaughter his young daughters, wife and unborn child.
At the time of sentencing, Judge Marcelo Kopcow called the murders "the most inhumane and vicious crime that I have handled out of the thousands of cases that I have seen."
Watts buried his wife in a shallow grave and stuffed his dead daughters in oil tanks where he worked, officials previously said.
Their bodies were discovered days after the trio were reported missing from their home in Frederick, Colorado.
After the trio 'vanished', Watts made a tearful TV plea to find them.
Days later, on August 15, he was arrested but denied he had killed them.
But things then took a sinister turn and he repeatedly changed his story to police.
He claimed that his wife had strangled their daughters in revenge after he revealed he was having an affair and wanted to split.
He allegedly told detectives that he flew into a rage and strangled Shanann after catching her in the act on a baby monitor screen.
But police rejected his web of lies.
The young girls' bodies were found on the property of Anadarko Petroleum, one of Colorado's largest oil and gas drillers.
Shanann's body was found in a shallow grave nearby.
A year on from the brutal slayings, which shook the world, Watts has said he wishes he could "make up" for what he did.
His mother Cindy Watts has also spoken out in a rare interview and shared a letter he sent her in which he says he has 'found God'.
“I’m still a Dad! I’m still a son! No matter what," he writes.
“Now, I can add servant of God to that mix! He has shown me peace. Peace, love, and forgiveness, and that’s how I live every day.”
The love rat, who was having an affair with colleague Nichol Kessinger, also claims if it wasn't for his mistress 'having a hold over him' he might not have committed the murders.