'Making a Murderer' prosecutor Ken Kratz is writing a book about the case and asked Steven Avery to confess

Ken Kratz, the prosecuting attorney in the trial of "Making a Murderer" subject Steven Avery, is writing a book.

The former district attorney of Calumet County, Wisconsin, told WBAY-TV that he has wanted to write the book since Netflix released "Making a Murderer" on December 18, "because the one voice forgotten to this point is Teresa Halbach."

Halbach, a photographer, was murdered in 2005. She was last seen alive at the Avery family's property and auto salvage yard. Steven Avery is serving a life sentence for her murder.

Kratz said that he's "finally grateful to tell the whole story," according to the Greenbay, Wisconsin, ABC affiliate.

That story, though, won't include an interview with Avery. Kratz attempted to visit Avery in jail to interview him for the book. In a letter to the convict, Kratz expressed disappointment that Avery decided to pass on his offer.

Avery's new attorney, Kathleen Zellner, shared Kratz's letter on Twitter. It was clear she didn't think much of the offer.

"Kratz letter to SA: Confess so I can write book & profit. This bloodsucking gives vampires a bad name," she wrote.

In the letter, Kratz referred to Avery's continued claim of innocence in the Halbach murder as "nonsense."

"Since I'm the only person who probably knows more about your case than anyone else, I hoped that you would choose me to tell your story to," Kratz wrote. "Unfortunately, you only want to continue your nonsense about being set up. That's too bad, because you had one opportunity to finally tell all the details, but now that will never happen."

Avery is currently appealing for a new trial. As seen in "Making a Murderer," Kratz resigned from his post as Calumet County district attorney after it was discovered that he had been sending sexual text messages to former clients, several of whom were victims of assault and domestic abuse.