Wichita ? When Wichita police announced they had arrested the BTK serial killer, Robert Beattie had to change the ending of the book on the case that he’d been working on for more than two years.

“My last line was, ‘He’s still out there,”‘ Beattie said. “That’s not my last line any more.”

Dennis Rader, 60, of Park City, was arrested and charged March 1 with 10 counts of first-degree murder, and police said they believed he was BTK. He is being held on $10 million bond and is scheduled to be in Sedgwick County District Court for a preliminary hearing April 19.

The BTK killer, whose nickname stands for “Bind, Torture, Kill,” has been linked to 10 slayings between 1974 and 1991 in the Wichita area.

Beattie added a final chapter to “Nightmare in Wichita: The Hunt for the BTK Strangler,” and his 333-page book arrived in Wichita bookstores Friday. It’s being sold online and is expected to be at other big book retailers this week.

While more books are sure to come, it’s the first BTK book to be published. It was scheduled to be released this summer, but was put on the fast track after Rader’s arrest, according to Beattie’s editor.

“Bob has been working on this for years, and he’s the authority on this. We didn’t want another book out there before his,” Martha Bushko of New American Library in New York said.

Beattie had sent his publisher the last edition of his book days before Rader was arrested. The Wichita lawyer was given five days to write an epilogue. Beattie, 48, said the ending wrote itself.

The book has pages of never before publicized stories surrounding the case.

Among them is an account of how police tried to use satellite photographs to identify BTK in the 1980s; another tells of Rader once applying for a job as a Wichita police officer, only to be rejected.

It also reveals that Lt. Ken Landwehr, the lead investigator in the case, was the target of a death threat that was included in a package the killer left in a UPS box Oct. 22.

“It was another one of his lyrics or poems,” Beattie said. “‘Death to Landwehr’ was the key line.”

Landwehr and police spokeswoman Janet Johnson declined to comment on the reported threat or any other portions of Beattie’s book.

Beattie said he conducted more than 400 interviews with more than 150 people familiar with the case.

Once BTK reemerged last year, some people he had interviewed wanted their names removed, fearing the killer would come for them. Beattie said others, including some detectives, were finally willing to talk about the case when BTK began communicating again.

“Once they realized he was still alive, they wanted to be sure the story was told correctly,” Beattie said.