A letter sent last week to The Wichita Eagle contained information on a 1986 killing and included photos that appeared to be of the victim's body. Police are examining the letter for DNA and other evidence.
"The photographs appear to be authentic," said Lt. Ken Landwehr, who has been working the BTK case for 20 years. "I'm 100 percent sure it's BTK."
More than two decades ago, the BTK Strangler claimed responsibility for seven slayings between 1974 and 1979; six victims were strangled, one was stabbed to death. Four were members of one family — two children and their parents.
"He's been a terrorist here for 30 years," author Robert Beattie said Friday on CBS News' The Early Show.
In his letters claiming responsibility for the murders, the killer used the initials "BTK" to refer to "bind, torture and kill." The claims were sent to the Eagle and TV station KAKE, the last one in 1979.
On March 19, the Eagle received a letter that contained a photocopy of the driver's license of Vicki Wegerle, 28, a wife and mother of two who was strangled in her home in 1986, nearly a decade after the unsolved 1970s serial killings, reports CBS News Correspondent Bob McNamara.
Three pictures showed the victim's body in various poses.
Until now, there was no suspicion that the slaying was the work of the BTK Strangler.
Wegerle's relatives said the driver's license was the only thing they know of that was missing from the home.
The letter was mailed in Wichita, Landwehr said Thursday. Since local TV stations aired reports on the letter Wednesday, more than 30 tips have been called in to police.
Landwehr said the new letter contained no suggestion that the killer planned to strike again.
"They're looking at all their old suspects again, people that they had cleared," said Beattie. "This all happened more than a decade before DNA was available.
"He'll watch and wait and see what the response is, and then, based on that, I wouldn't be surprised if we heard from him again," former FBI profiler Gregg McCrary told CBS News.
Detectives also are looking through lists of inmates who have recently been released; they said the reason they have not heard from the BTK Strangler since 1979 could be that he was in prison.
"This is going to be homicide's top-priority case," Landwehr said.
The return address on the letter said it was from Bill Thomas Killman — initials BTK. The address appeared to refer to a now-vacant building.
Norma Wegerle, a sister-in-law of the slain woman, said relatives often wondered whether the BTK killer could have been involved in the case.
She said that while the new development raised hopes that the case might be solved, she also was saddened by the reopening of old wounds.
"We just want it to be solved so we can get closure," she said.
The father of victim Nancy Fox, 25, wants more than closure.
"I hope this old guy, if he is here, he's made the biggest mistake of his life by coming forward at this time," Dale Fox told CBS affiliate KWCH.