BTK Suspect a 'Hateful' Man, Former Co-Worker Says

To Mary Capps, Dennis Rader (search) was a power-hungry jerk and a nightmare of a boss. Having already filed three complaints against him, she was in the middle of a fourth when police announced Rader was the long-sought BTK serial killer (search).

As horrifying as it was to learn that the man she had been answering to for six years might be a vicious murderer, Capps said she wasn't exactly shocked.

"The day after he was arrested, I was so mad. I wanted to stand in front of that city council, in front of the department heads and every one of the employees. I wanted to say, 'See?'" she said.

Rader, 59, was arrested on Feb. 25 after DNA tests (search) linked him to at least eight killings committed between 1974 and 1986. Authorities are confident his arrest has brought to an end a 31-year manhunt for the serial killer who terrorized Wichita in the 1970s.

For years, Rader and Capps were the only two compliance officers in Park City, Kan. And according to Capps, the code enforcer's inflated ego often spun into delusions of grandeur.

Rader once designed a rain slicker with the word "Police" on the back and wore it on the job — even though he was not a police officer and did not have the power to arrest people, Capps said.

"The [police] chief went over and ... just raised Cain. Dennis got mad and said, 'Fine ... just get me a new one and put 'Dogcatcher' on the back of it,'" Capps recalled. "I mean, he was just mad that he couldn't put 'Police' on the back of it."

The incident was one of several that Capps attributed to an anti-social personality.

"He's hateful, condescending, egotistical, and he just does not work well with other people," she said.

Capps filed a complaint against the city with the Kansas Human Rights Commission that alleges discrimination and a hostile work environment.

People who know her told FOX News that city administrators dismissed her complaints because she was a woman. More seriously, friends said Rader once locked her in his office and rushed at her, but she was able to get behind a table and call for help. Capps could not comment on that allegation.

Shortly after Rader's arrest, residents described him as an unpleasant, nosy man who went to great lengths to nab them for violations. But others praised him as a church and Cub Scout leader.

As angry as she is, Capps said she feels badly for Rader's wife, who didn't seem familiar with her husband's darker side.

"He would become a softer, more gentle person when he was speaking to his wife or his wife was around," Capps said. "He would turn into Ward Cleaver."

Capps told FOX News she is haunted by what might have happened to her had Rader managed to fool police the way he apparently did his wife.

Click in the video box above for a full report by FOX News' Carol McKinley.