A dramatic 10-second video released this week by aid worker Kayla Mueller’s family showed the woman pleading for help shortly after Islamic State fighters kidnapped her in Syria in 2013.

The brief clip served as her proof-of-life video. U.S. officials confirmed last year she was killed. The cause of her death remains murky, though ISIS claimed a Jordanian airstrike killed her.

“My name is Kayla Mueller… I need your help,” she was reported as saying in the video. “I’ve been here too long, and I’ve been very sick. It’s, it’s very terrifying here.”

A friend of Mueller’s reportedly received the video and gave it to the FBI. Investigators then sent the video to the aid worker’s parents, who gave it to ABC News. The video reportedly serves as the only images of Mueller in captivity.