It was not one single clue that finally led police to Dennis Rader, the alleged BTK killer. (The name, chosen by the killer, stands for "Bind, Torture, Kill.")
"He was caught with good old-fashioned police work coupled with application of forensic techniques," said investigative consultant Vernon Geberth.
Rader has confessed to at least eight of the 10 murders that police say he committed between 1974 and 1991.
He first came under suspicion in 1974, when BTK sent death fantasy letters and poetry to the media. They were copied on a machine at Wichita State University, which yielded a pool of student suspects, including Rader. But the killings and the communication suddenly stopped.
Last March, after 25 years, BTK left new evidence -- again at Wichita State University. As a result, Rader became a suspect again.
"Had he not re-emerged," said Geberth, "the police wouldn't have had that very important forensic evidence to link eventually to the BTK killer. Mr. Rader was below the radar."
Two weeks ago, BTK dropped off a package at Kansas television station KAKE, which included a floppy disk linked to a computer at Rader's church.
"They asked me if I had a list of people who had access to our computer and I provided a list of people for them," said the Rev. Michael Clark of Christ Lutheran Church. "Yes, [Rader] was [on that list]."
Many local residents are stunned by how much access Rader had to the community. He worked installing burglar alarms when most of the killings occurred. Investigators long suspected BTK was able to easily enter victims' homes.
With the evidence piling up, investigators obtained a sample of Rader's DNA. It matched DNA collected at BTK's first crime more than 30 years ago.
"That's what leads to the downfall of serial killers," said James Fox, co-author of "Extreme Killing: Understanding Serial and Mass Murder." "They feel so invincible, so unstoppable, that they make an important error that eventually leads to their capture."
Investigators say this case is a reminder to follow evidence more than the criminal profiles.
"One of the things I think we need to do now is learn from him," said former Wichita police Chief Richard Lamunyon. "We need to know why he did it, how did he pick his victims, what drove him."
Rader is married with children, a city worker, a church official and Cub Scout leader. He hardly fits the stereotypical profile of an antisocial serial killer.
"In reality, most serial killers look like the man next door," said former FBI behavioral scientist Peter Smerick. "They do not look like Charles Manson."
According to criminologists, at any given time there are at least 25 to 100 active serial killers in the United States. The FBI is currently assisting in 16 such cases.
Law enforcement officials now say they will use this case to reassess their investigations of unsolved serial killings around the country.
ABC News' Barbara Pinto filed this report for "World News Tonight." ABC News' Pierre Thomas contributed to this report.