Gillian Luchejko, a 46-year-old client services manager in New Jersey, first found out her sister Pamela Elarabi posted a photo of herself on the social-networking site Facebook as she prepared to take her own life when it appeared on the top of Luchejko’s own feed.

On the evening of Friday, June 22, around 9 p.m., after several cryptic text posts on her page throughout the day, Elarabi posted an image in which she appeared to be attempting suicide. The photo was public, so anyone looking at Elarabi’s Facebook page could see it.

Elarabi had been publishing increasingly despairing status updates on her page in the preceding months, Luchejko said, so her sister was not sure what to make of the image. She called their brother and asked him to check on Elarabi, who had struggled with suicidal thoughts and depression for most of her life.

Luchejko wasn’t the only one who found the post alarming. By the time her brother arrived, paramedics were already on the scene — a neighbor had seen the image and called 911. Elarabi was rushed to the hospital, where she died on June 23. She was 49.

While Elarabi’s siblings decided whether to turn off her life support, the disturbing image of her last moments remained visible to her 792 Facebook friends.

In the midst of the chaos that evening — while Elarabi’s siblings were deciding whether to remove life support, breaking the news of her death to her two adult children, and making arrangements for a burial — the disturbing image of Elarabi’s last moments remained on Facebook, visible to her 792 friends, and anyone who visited her page.

“People kept texting us, asking what was going on, and what the Facebook post was about, and I was thinking, ‘I can’t answer you right now because she is dying,’ ” Luchejko told MarketWatch. “Everyone felt helpless.”

Facebook friends wrote, ‘What’s going on? Are you OK?’

But it took more than 72 agonizing hours to get the photo taken down. Luchejko said the family considers itself relatively private, and was horrified to watch the news of her sister’s death spread across their small hometown and the Facebook community.

The experience highlights the painful challenges that social-media companies like Facebook FB, +0.89%[1] and their users must confront as more people put practically their entire lives online. Facebook walks a fine line between intervening and saving lives while avoiding censorship. The company has the ability to step in when users appear poised to hurt themselves, but as Elabari’s case shows, it doesn’t always act in a timely manner even in the aftermath of tragedy.

With limited cellphone service in the hospital, Luchejko...

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