The so-called "Islamic State" has murdered a Second American reporter, releasing a**ther propaganda video Tuesday showing a masked militant with a British accent cutting the throat of a US captive. In the latest footage, 31-year-old reporter Steven Sotloff addresses the camera to say he is a victim of President Barack Obama's decision to press on with air strikes against the jihadists. A US spokeswoman said Washington was trying to authenticate the "sickening" footage, and British Prime Minister David Cameron said it depicted an "absolutely disgusting, despicable act." The footage was almost identical to a video the Islamic State released last month in response to Obama's ordering US air strikes, and showing the murder of 40-year-old reporter James Foley.