The Colorado man who butchered his pregnant wife and two toddler daughters told police he was “not a good man” as he confessed to coldly dumping their bodies in a “freakin’ oil tank,” according to documents released this week.

Notes from interviews released Wednesday by the Weld County District Attorney’s Office show how investigators got Christopher Watts, who was sentenced to life in prison last week for the heinous killings, to confess after he failed a polygraph test.

For two days, Watts, 33, maintained that he had no clue what happened to his wife, Shanann, 34, and their two daughters, after they went missing on Aug. 13.

He told investigators he missed reading to Celeste, 3, and Bella, 4, and that it was difficult to be at home without them, the documents, posted by The Denver Post show.

When the interviewer, at one point, asked Watts to describe all the ways a person could make someone disappear, the Watts gave a short answer — and then giggled.

In a polygraph test, Watts didn’t tell the truth each time he answered “no” to whether he physically caused his wife to disappear, if he was lying about the last time he saw her, and whether he knew where Shanann was.

Later, Watts admitted he was having an affair with a woman named Nichol Kessinger, the documents show. Investigators told him to be honest and “get everything off his chest.”

That’s when Watts asked to speak to his father, Ronnie Watts, who was in the police department lobby.

“She hurt them,” Watts told his dad, according to the documents. “And then I freaked out and I hurt her.”

Weld County District Attorney Michael Rourke called the explanation that Watts killed his wife after she murdered their daughters a “flat-out lie” after Watts pleaded guilty to all three murders.

After Watts spoke to his dad, investigators spoke with him for six hours, pressuring him into telling them where the bodies were hidden.

“I’m not a good man,” Watts said, as he apologized for lying to investigators.