Ex-Wife of Man in Prison for Third Wife's Murder Details Their 'Abusive' Marriage

"I had hoped that things had changed," she said.

— -- The former wife of a North Carolina man in prison for his third wife’s murder says he once told her he would kill her during their marriage.

"He said if I ever tried to take his daughter away from him, that he would kill me," Amanda Casey told ABC News’ "20/20" of former husband Michael Wilkie.

Casey said she finally left Wilkie after four years. Wilkie, the father of Casey’s younger daughter, was found guilty of first-degree murder in January for the 2012 death of his wife Shelby Wilkie, whom he married after separating from Casey. Michael Wilkie is serving a life sentence without parole.

Like the late Shelby Wilkie, Casey, who lives in North Carolina, met Michael Wilkie through an online dating site.

"He was very friendly, very charming, easy to talk to, very soft spoken, and he had a good job and seemed to be pretty good," Casey said.

Casey said after dating for a year and a half, they married in 2004. But a couple months after their wedding, Casey said Michael Wilkie started trying to control what she did and where she went. She said he also alienated himself from Casey’s daughter from a previous marriage.

"If I planned to do something with one of my friends, he would manipulate the situation, and there would be something that came up that would interfere or get in the way," Casey recalled.

Casey said Wilkie even once attacked her when she was pregnant with their daughter.

"He was physically abusive at that time," she said. "He grabbed me around my throat and threw me around our bedroom and on the bed. My shoulder went through and made that hole in the sheetrock in the bedroom."

Casey never reported the incident to police, and charges were never filed. Michael Wilkie's lawyer has not returned to ABC News' multiple requests for a comment.

Michael Wilkie's friends and Casey’s family were not aware of the darker side to his personality, Casey said.

"Because he was so good at masking. It was like Jekyll and Hyde: two personalities and you didn't know which one you would get," Casey said. "You didn’t know which one. You would meet when you got home."

Casey kept a journal documenting her life with Wilkie that included dates, names and even addresses.

"I had thoughts [that he would kill me] mainly because he told me he would kill me," she said. "I knew it was a possibility and … that’s always in the back of your mind."

Still, Casey said she didn't give up hope for their marriage.

"I am the type of person that I will stay in a situation, whether it’s a job or a marriage … longer than I should because I don’t give up hope easily," she said. "And I am always thinking about, ‘What could I do to make it better?’"

After they had an argument about pictures she at taken of their two daughters together, Casey said she finally left Wilkie one night in 2006. She took her older daughter, who had been terrified of him, but left their 3-year-old behind. They divorced in 2008.

Casey remarried and got joint custody of their 3-year-old, and she eventually met Wilkie's next wife, Shelby Wilkie, at a school event for Casey and Michael Wilkie’s daughter. Despite what she said she went through during their marriage, Casey said she didn't think of warning Shelby Wilkie.

"I had hoped that things had changed, and that it was me and not, you know, him. And that way, hey, he could be happy. She could be happy, and it could be a nice household environment."

But Casey said she spoke to Shelby Wilkie just a few months before she was reported missing in January 2012.

"She said, ‘I just want to ask you some things about Michael, is that OK?’" And I said, ‘Sure,’" Casey recalled. "And I said, ‘Shelby, if there is anybody that knows what you are going through, it’s me."

Casey said she had an appointment to keep and asked Shelby Wilkie to call her back. But the next time Casey heard Shelby’s name, it was on the TV news when her former husband was pleading for Shelby to come home.

"I turned around to my husband, and I said, ‘She ran [from Michael Wilkie]. I know she ran,’" Casey said.

It wasn't until Michael Wilkie's arrest for Shelby Wilkie's murder that Casey said she stopped feeling terrified of her former husband. Casey said she has moved on.

"It’s made me grow as a person,” she said. “And it has made me stronger as a human being.”

Help and information for victims of domestic violence is available 24/7 through the National Domestic Violence Hotline by calling 1.800.799.SAFE or visiting their website HERE.

For more resources on ways to stop domestic violence among teens and women, click HERE.