Chilling video shows American ISIS hostage Kayla Mueller shortly after she was kidnapped

never-before-seen video published Thursday shows 25-year-old Kayla Mueller pleading for help after she was kidnapped by the terrorist group ISIS.

Mueller, who was an aid worker in Syria, was kidnapped in 2013. US officials confirmed her death in 2015.

In the video, which Mueller’s family released to ABC News, Mueller is seen wearing a black hair covering, looking thin compared to photos of her from before she was captured.

“My name is Kayla Mueller,” she said in the video, intended to be proof of life for her family and friends back in the US.

“I need your help,” she continued. “I’ve been here too long, and I’ve been very sick. It’s, it’s very terrifying here.”

The video echoes later ISIS productions that are known for their slick editing and high quality. Chris Voss, a retired FBI chief hostage negotiator who viewed the video, explained why this is.

“You look at this video, and right away you can see a number of things. Basically from a pure physical health standpoint, she’s not in bad shape physically. They’re letting us see that,” Voss told ABC. “They want us to see that overall, she’s not in bad shape. They probably put makeup on her before they shot the video. They produce these the same way any media company produces videos.”

Voss speculated that ISIS had Mueller rehearse what she was going to say.

“They probably rehearsed that a number of times,” Voss said. “I would imagine they shot that anywhere from no less than five times, maybe as many as 15 times. They rehearsed her. They got the lighting right. They controlled what’s in the background. They controlled everything they said. Everything she said. … They want to put enough out there to start a negotiation. And that’s what this is intended to do.”

One of the terrorists who took Mueller hostage in Syria emailed the video to one of her friends in the US, who then forwarded it to the FBI. The video came about three weeks after Mueller was taken.

ISIS was hoping to earn ransom money from holding Mueller hostage. But the US has a policy against paying ransoms to terrorist groups, who often kidnap Westerners to extort money they use to fund their operations.

This video wasn’t the only message Mueller sent to the outside world while she was in ISIS captivity.

She also wrote a heartbreaking letter to her family before she died.

“Just the thought of you all sends me into a fit of tears,” she wrote. “If you can say that I have ‘suffered’ at all throughout this whole experience it is only in knowing how much suffering I have put you all through; I will never ask you to forgive me as I do not deserve forgiveness.”

Mueller’s family also received an audio clip in 2014. She explained what her captors wanted in exchange for her safe return.

“Mum and Dad, I still am remaining healthy,” she said in the recording, according to ABC. “You should have already received the three answers to the proof life questions you provided. Those detaining me are demanding an exchange of Dr. Aafia Siddiqui’s release for my release. If this is not achievable, they are demanding 5 million euros to ensure my release.”

ABC News spent two years investigating the kidnapping and imprisonment of Mueller at the hands of ISIS. Their special report is airing on “20/20” Friday at 10 p.m.

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