Throughout the hunt for Steve Stephens, the fugitive who shot and killed an elderly Cleveland man on Sunday and posted the video to Facebook, a mysterious figure was always in the background of the story: his ex-girlfriend, whom he blamed for the mental state that led to the horrifying execution.

The woman, whom NBC News isn't naming because police haven't officially released her identity, said in an extensive interview that she was stunned and devastated as she watched the man she'd loved boast on Facebook of targeting people for death because of her.

The woman, a 42-year-old social worker who has a master's degree in social administration and teaches at a university, said she and Stephens had recently been looking for wedding rings when, suddenly, he called her on Saturday to say they were through and to tell her to "throw away his stuff."

Steve Stephens in a combination of stills from a video he broadcast Sunday on Facebook in Cleveland. Facebook via Reuters

Sunday, Stephens uploaded the video of his murder of Robert Godwin, 74 — whom he ordered to say the woman's name on camera before killing him.

"She's the reason that this is about to happen to you," he told Godwin in the video.

By Tuesday, Stephens also was dead, having committed suicide as police closed in on him in Erie, Pennsylvania.

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While Stephens alone is responsible for the episode, the woman told NBC News that the easy publicity he was able to attract on Facebook likely escalated the crisis.

The woman said "my mouth fell open" as she watched her ex stream live video from in front of her workplace, detailing "this is where [she] works and what he was about to do."

The woman said it was clear to her that Facebook's video features were "something that was meant to be good [but] was perverted bad."

"I'm a clinician," she said. "I'm in the mental health field and I teach, and we have a session in my class and we talk about media and how the use of media has been has almost been perverted.

"What it's being used for is not what it was intended to be used for," she said.

Cleveland Police Chief Calvin Williams agreed, telling reporters: "This is something that should not have been shared around the world. Period."

Please please please stop retweeting that video and report anyone who has posted it! That is my grandfather show some respect #Cleveland — Ryan A. Godwin (@god_winr) April 16, 2017

Facebook didn't help matters when it initially issued a brief statement saying, "This is a horrific crime and we do not allow this kind of content on Facebook."

Under pressure for having described a real-life murder as "content," the company soon issued a longer statement, reassuring users: "We are reviewing our reporting flows to be sure people can report videos and other material that violates our standards as easily and quickly as possible."

"We disabled the suspect's account within 23 minutes of receiving the first report about the murder video, and two hours after receiving a report of any kind," it said. "But we know we need to do better."

Monday, Facebook's co-founder and chief executive, Mark Zuckerberg, echoed the statement in remarks at the company's F8 developers conference in San Jose, California, saying: "Our hearts go out to the family and friends of Robert Godwin Sr., and we have a lot of work — and we will keep doing all we can to prevent tragedies like this from happening."

None of that lessens the pain for Stephens' ex-girlfriend and her three daughters, all of whom, she said, "loved Steve." While the woman has been strongly supported on social media, there has also been a small but savage undercurrent that presumes she's to blame.

"No disrespect but if somebody had to die it should've been" her, read one tweet. "Is it [messed] up that i think that guy should just kill [the woman] instead of all those other people ... ?" read another. Her name even became a hashtag attached to the word "massacre."

"Now I'm just kind of existing," she said. "I'm not living at the moment. I'm just existing."