Who is Steven Sotloff, the other US journalist being held by IS?

The family of journalist Steven Sotloff is asking the White House to do everything it can to free him.

Sotloff is the man believed to be the person who appears at the end of an Islamic State video showing the beheading of fellow American journalist James Foley.

He is seen with his head shaved and wearing an orange jumpsuit similar to Foley's. He is dragged into the frame by a masked militant, who demands President Barack Obama ends military airstrikes against ISIL.

"The life of this American citizen, Obama, depends on your next decision," the unidentified militant says.

• The botched mission to rescue Foley

• Paper's front page photo of James Foley sparks outrage

• James Foley's mother pays tribute to her "extraordinary son"

In a Facebook message, Frank Castle, the boyfriend of Sotloff's sister, asked supporters to sign a petition calling for his release.

"MY GF Lauren Sotloff's brother Steven Sotloff was taken hostage by ISIS on August 04 2013 and up to this point it has been all under wraps," Castle wrote.

"People please not only sign the following petition, but PLEASE SHARE soo the more the better. Thank you in advance & pray for his safe return home."

Lauren Sotloff did not immediately return a Facebook message seeking comment.

Steven Sotloff, a freelance journalist from Miami whose work has appeared in Time magazine, Foreign Policy and the Christian Science Monitor, went missing in Aleppo, near the Syrian-Turkish border.

Sotloff's last published piece appears to be a July 2013 column about Egypt ("Opposing Morsi but Defending Democratic Legitimacy") for World Affairs magazine:

As I stumbled over the sandals and the men sleeping next to them at the Raba’a al-Adawiyya mosque in Nasser City, where the Muslim Brotherhood is holding its daily rallies, the beards and headscarves blended into a blurry monochrome pastel. But as I looked closer into a sea of Egyptians that Moses would have been hard pressed to part, one man’s tresses caught my attention. A cross between Don King’s stand-at-attention locks and Julius Erving’s flapping waves, they drew me in like a siren call.

His last piece for Time (Libya’s New Crisis: A Wave of Assassinations Targeting Its Top Cops) was published in late 2012.

A friend, Ann Marlowe, tweeted that Sotloff "lived in Yemen for years, spoke good Arabic, deeply loved Islamic world.. for this he is threatened with beheading."

According to his LinkedIn profile, Sotloff is a graduate of the University of Central Florida. His Twitter bio says he was last based in Libya; his most recent tweet, on August 3, 2013, is about the Miami Heat.

A few days before, Sotloff tweeted that he had been pepper-sprayed by police in southern Turkey.

On July 27, 2013, Sotloff posted a photo of himself posing with two children in front of a car adorned with Libyan flags (and a New York Yankees decal, placed upside-down) on his Facebook page.

He used Instagram far less frequently. In December 2012, he posted several photos of children from a Syrian refugee camp.

On Wednesday, President Barack Obama said he was “heartbroken” by the beheading of Foley but vowed to press on with US military operations to cut the “cancer” of IS out of the Middle East.

“Jim was taken from us in an act of violence that shocks the conscience of the entire world,” Obama said from Martha’s Vineyard, where he is on vacation.

The president did not mention Sotloff by name.

“The United States of America will continue to do what we must do to protect our people," he said. "We will be vigilant and we will be relentless. When people harm Americans anywhere, we do what’s necessary to see that justice is done."

News break – August 21