(NewsNation) — Rex Heuermann, who is accused in the Gilgo Beach killings, has reportedly been exchanging letters from prison with Keith Jesperson.

Jesperson, known as the “Happy Face Killer,” was convicted in the murders of eight women. He got his nickname by drawing “happy faces” on many of his letters to the media and authorities before being arrested in 1995.

NewsNation’s Laura Ingle interviewed a podcaster who put her in contact with Jesperson. He wrote her five double-sided, handwritten letters from Oregon State Penitentiary.

“I told him to own all his crimes,” Jesperson said in one letter. “All of them.”

Heuermann, for his part, has pleaded not guilty to all charges against him.

A few weeks ago, Ingle spoke to Jesperson on a recorded line at the prison. During the interview, Jesperson continued urging Heuermann to confess.

“If he doesn’t come clean, it’s gonna go to trial,” Jesperson told Ingle. “They’re going to present all the evidence that they have on him to convict him.”