His murderer spoke with a British accent, like James Foley’s killer. It is unclear if it is the same man, who has been nicknamed Jihadi John.
The masked killer in the video also issued a threat against a hostage he said was British and said: “We take this opportunity to warn those governments that have entered this evil alliance with America against the Islamic State to back off and leave our people alone.”
He added: “I’m back, Obama, and I’m back because of your arrogant foreign policy towards the Islamic State.”
‘Disgusting, despicable act’
The White House said it could not confirm the authenticity of the video. Prime Minister David Cameron said the video was an “absolutely disgusting, despicable act”, and he would be making a statement later.
State Dept spokeswoman Jen Psaki said the US intelligence services would “work as quickly as possible to determine its authenticity”, adding: “If the video is genuine we are sickened by this brutal act taking the life of another innocent American citizen. Our hearts go out to the Sotloff family.”
The last moments of James Foley, a journalist like Sotloff, were also uploaded to the web. Sotloff featured in the Foley video, with his killer warning that his life was at risk.
Sotloff, 31, was abducted in northern Syria a year ago while reporting the civil war there. His mother Shirley appealed on 29 August in a video message to Islamic State’s self-proclaimed caliph, Abu Bakr al-Baghdadi, for her son’s release.
Before he went missing, Sotloff posted a number of messages about the turmoil in the country, but also about his favourite US basketball team, Miami Heat.
The video showing the killing of Foley, 40, was released on 20 August and featured Sotloff kneeling in an orange jumpsuit.
It ended with a warning to President Obama that his fate “depends on your next decision”. Since then, the US has continued its air strikes against IS in Iraq.
The Foley video was titled A Message to America, while the Sotloff video is called A Second Message to America.
Sotloff’s university friend, Josh Polsky, is quoted in the New York Times as saying: “The guy lit up a room. He was always such a loyal, caring and good friend to us.”