Diane Staudte.

diane-staudte-2-2000

In 2013, after two members of his congregation died under mysterious circumstances, Pastor Jeff Sippy placed an anonymous call to the police in Springfield, Mo.

“I shared that I am a pastor and I have a family who has experienced two deaths in a short proximity of time and has another family member in ICU,” Sippy, the pastor of Redeemer Lutheran Church, says on this week’s episode ofABC’s20/20.

“I’ve never had two family members die in the same type of situations ever,” he tells20/20.

“I believe these were circumstances that needed to be investigated,” he says. (An exclusive clip from his interview is shown below.)

Sippy’s sharp instincts ultimately led to the arrest ofDiane Staudte, the mother of four who plotted to poison her husband and two of her children with antifreeze.

Her husband, Mark Staudte, died on Easter Sunday in 2012 of what appeared to be natural causes. Five months later, her son, Shaun Staudte, was found dead in their home after suffering from flu-like symptoms.

In June of 2013, Diane’s daughter Sarah Staudte was admitted to the ICU with a brain bleed and organ failure. Doctors started to think she had been poisoned somehow.

Want to keep up with the latest crime coverage? Sign up forPEOPLE’s free True Crime newsletterfor breaking crime news, ongoing trial coverage and details of intriguing unsolved cases.

Springfield Police Department Detective Neal McAmis brought Diane and her daughter Rachel Staudte in for questioning.

Diane entered an Alford plea for the two counts of first-degree murder, which acknowledges that prosecutors have enough evidence to convict him without her having to admit to the crime. She is serving a life sentence without parole.

Rachel pleaded guilty to second-degree murder in 2015 as part of a plea deal in exchange for testifying against her mother. She received two life terms with the possibility of parole after 42-and-a-half years.

rachel-staudte-2000

But now, in an exclusive interview with ABC News senior national affairs correspondent Deborah Roberts, Diane claims that she is innocent.

“I said what I was told to say — I’m saying there’s more to that than what people know,” Staudte said in an exclusive interview with20/20.

“Mark was with some people that are very dangerous — people have disappeared,” she told Roberts.

Telling Roberts she heard in prison that someone put a hit out on Mark, she said, “I’m saying somebody probably came in and gave him something.”

Photos of Diane and Rachel Staudte from her Facebook account.

Photos of Diane and Rachel Staudte from her Facebook account

Diane never said anything about Mark knowing any “dangerous people,” say authorities.

In Friday’s20/20, Diane talks for the first time about her relationship with her family and her feelings about the shocking deaths that changed their lives forever.

It also features an interview with Sarah from the ABC News archives about how she is healing after her mother and sister’s betrayal.

Watch the full20/20episode on Friday (9:01-11:00 p.m. EST) on ABC, and the next day on Hulu.

source: people.com