Dennis Rader lived in a suburb of Wichita with a wife and two children, led a Cub Scout troop and was active in his Lutheran church.
But police say he is also the serial killer who called himself BTK - for "Bind, Torture, Kill" - and is responsible for the deaths of ten people, mostly young women, since 1974, reports CBS News Correspondent Cynthia Bowers.
As an ordinance enforcement officer for the local government, Rader could be seen measuring grass in a front yard with a tape measure to see if it was too long, a neighbor said.
He was also in charge of animal control since about 1990, the Wichita Eagle reports, and served in Vietnam.
Although no charges have been filed, a jubilant collection of law enforcers and community leaders told a cheering crowd they were confident the long-running case could now be closed, ending a 31-year manhunt.
Authorities generally declined to answer questions in detail after announcing the arrest, but Kansas Gov. Kathleen Sebelius told The Associated Press that DNA evidence was the key to cracking the case.
Wichita television station KAKE, citing unnamed sources, reported that DNA from Rader's daughter, Kerri, was instrumental in his capture. On Sunday, KAKE anchor Larry Hatteberg told CNN that the source said Rader was already under surveillance when his daughter's DNA was obtained.
BTK stoked fears throughout the 1970s in Wichita, a manufacturing center with 350,000 residents, with his grisly crimes and taunting letters sent to police and media.
He even phoned in one of his killings, saying: "Yes, you will find a homicide at 943 South Pershing Street, Nancy Fox."
The killer stopped writing in the late 1970s but resurfaced about a year ago with a letter giving details of a 1986 slaying that had not previously linked to BTK.
In Park City, the suspect's neighbors said he helped elderly neighbors with yard work but described him as an unpleasant man who often went looking for reasons to cite his neighbors for violations of city codes.
Bill Lindsay, 38, lived behind Rader and said his wife caught Rader in their adjoining backyards filming the back of their house.
"He really acted really funny," said Lindsay, a truck driver. "I'd be on the road and my wife would tell me, 'Dennis has been out again, taking his pictures.'"
Jason Day, 28, said his brother was in Rader's Cub Scout pack at the nearby Park City Baptist Church, but their mother pulled him out because of Rader.
"It was his demeanor," he said. "He was so strange."
Messages left for Rader's family members were not returned on Saturday, and no one answered the door at the home of his in-laws.
Rader was being held at an undisclosed location, and it was not immediately clear if he had a lawyer. In Kansas, suspects generally appear before a judge for a status hearing within 48 hours of their arrest.
Prosecutor Nola Foulston said the death penalty would not apply to any crime committed between 1972 and 1994, when Kansas did not have the death penalty.
The BTK slayings began in 1974 with the strangulations of Joseph Otero, 38, his wife, Julie, 34, and their two children. The six victims that followed were all women, and most were strangled.
Along with his grisly crimes, the killer terrorized Wichita by sending rambling letters to the media, including one in which he named himself BTK for "Bind them, Torture them, Kill them." In another he complained, "How many do I have to kill before I get my name in the paper or some national attention?"
In several of the letters, BTK included clues to his identity. Police had long believed BTK was a graduate of Wichita State University, as Rader was. Letters sent in the past year included jewelry that police believed may have been taken from BTK's victims and the driver's license of one of the victims.
"He obviously was getting rid of his trophies; he was leaving us a wide-open trail," said Richard LaMunyon, Wichita's police chief from 1963 to 1989. "I think the ultimate goal was of him being caught."
At one point, investigators made a list of white men who graduated from Wichita State in the 1970s. Officials said Rader's name likely was on that list, but he wasn't identified back then as a suspect.
BTK stopped communicating in 1979 and remained silent for more than two decades before re-establishing contact last March with a letter to The Wichita Eagle about an unsolved 1986 killing.
The letter included a copy of the victim's driver's license and photos of her slain body. The return address on the letter said it was from Bill Thomas Killman — initials BTK.
Thousands of tips poured in, and the Kansas Bureau of Investigation gathered thousands of DNA swabs in connection with the investigation. In the end, DNA evidence was the key to cracking the case, said Kansas Gov. Kathleen Sebelius.
"The way they made the link was some DNA evidence, that they had some DNA connection to the guy who they arrested," Sebelius said in an interview with The Associated Press. She did not elaborate.
The two newly identified cases were similar to the early ones with one exception, Sedgwick County Sheriff Gary Steed said: The bodies had been removed from the crime scenes. One of the victims lived on the same street as Rader.
"We as investigators keep an open mind. But only now are we able to bring them together as BTK cases," he said.
On Friday, investigators searched Rader's house and seized computer equipment.
Authorities, who generally declined to answer questions in detail after announcing the arrest, had little to say about why BTK resurfaced after years without contact.
"It is possible something in his life has changed. I think he felt the need to get his story out," LaMunyon said.