ISIS claims beheading of US aid worker Peter Kassig

The ISIS has beheaded another American -- a former Army Ranger and aid worker who had converted to Islam, the execution video released on Sunday purportedly shows.  Abdul-Rahman Kassig, 26, who was earlier called Peter, had been captured in October 2013, but had managed to send a letter to his family with a released hostage. That was his last contact with them.  Kassig, who is the third American to be executed by the Sunni militant group, appears in the video with the same ISIS terrorist as the one in all others. The militant was covered…