A video released on Tuesday purporting to show an American journalist being beheaded by militants from ISIS militant group in Iraq has "appalled" the U.S. "If genuine, we are appalled by the brutal murder of an innocent American journalist, and we express our deepest condolences to his family and friends," said White House National Security Council Spokeswoman Caitlin Hayden.Militants identified the victim as James Foley, a freelance journalist who went missing in Syria in late 2012 while working for the Boston-based GlobalPost. Hayden said U.S. intelligence is working to determine the authenticity of the video, which has been removed from the Internet. The victim is shown reading a message, addressed to a brother supposedly in the U.S, Air Force, stating U.S. airstrikes in Iraq were the reason for his death. "When your colleagues dropped that bomb, they signed my death certificate," the message said. Another missing journalist, thought to be Steven Joel Sotloff, was also pictured in the video as a threat that he could also be killed. A militant speaking in a British accent addressed U.S. President Barack Obama saying, "Any attempts from you, Obama, to deny Muslims their safety of living under the caliphate will result in the bloodshed of your people." The U.S. has conducted dozens of airstrikes on ISIS militants in Iraq since Aug. 7 in order to halt the militants' gains, especially in northern Iraq.