Kevin James Pettiford described it as his "inner monster", telling detectives he was eternally trapped in an internal struggle between good and evil.
"I know I am evil, right," Pettiford said during one of many police interviews. "But I always say calculated and controlled evil."
The 38-year-old, who taunted police and wanted to become Australia's most prolific serial killer, described his thinking before he killed homeless man Andrew Murray while he slept in a Tweed Heads park in November, 2019.
"I saw the person there," he said.
"I thought should I, shouldn't I, should I, shouldn't I. Back and forth, back and forth. Then boom, did it. Caved his head in. I just hit his head with the rock."
About two months earlier, Pettiford had used a rock to kill another homeless man, David Collin, as he slept in Maroochydore on the Sunshine Coast.
After his arrest, and when he chose to strike again, he targeted fellow Cessnock jail inmate Nathan Mellows because he said Mellows had "no one and nowhere to go when he got out".
Mr Mellows survived and Mr Pettiford later made admissions to the attempted murder, saying he targeted his victim's carotid and subclavian arteries because "death would follow very rapidly". He signed a letter to police with THOD, which he later said meant "the hand of death".
"I don't know, that is just the inner monster in me," he said. "That is the monster that has been in me for a f---ing long time. "Look, I know what I did was wrong. I can't f---ing help it, man. I tried."
On Wednesday, December 6, the 38-year-old Victorian vagrant and wannabe serial killer was found guilty of murder and causing wounding with intent to murder after a lengthy trial in NSW Supreme Court.
There had been no dispute that Pettiford struck Mr Murray with the rock and killed him or that he slashed the throat of Mr Mellows, but the issue for the jury to determine was whether or not he was suffering from a mental health impairment at the time of the attacks and whether he knew what he was doing was right or wrong.
Instead, he was convicted of murder and will be sentenced in February next year.
The court heard there is a murder warrant outstanding for Pettiford in Queensland and he is expected to face a similar trial in that jurisdiction at a later date.