NEW DELHI: The Islamic State released a video on Sunday purportedly showing the execution of American aid worker Peter Kassig. The video marks the execution of the fifth western hostage and third American by the group, following the deaths of US journalists James Foley and Steven Sotloff, and British aid workers David Haines and Alan Henning.

Kassig appeared at the end of video showing the death of Henning, which, going by the videos of executions released by the group, pointed to the fact that Kassig would be next in line. However, no hostage appears at the end of the Kassig execution video, which, in turn, marks a clear departure from the style of the previous execution videos.

The most significant departure is the beheading itself. The four previous videos have shown the hostages kneeling and forced to recite a message to their respective countries linking its actions to their capture and execution. “Hi, I’m Alan Henning. Because of our Parliament’s decision to attack the Islamic State, I as a member of the British public will now pay the price for that decision,” Henning said, facing the camera in the previous video. Similarly, Haines in his execution video addressed British Prime Minister David Cameron, whilst Foley and Sotloff address US President Barack Obama and link US airstrikes on IS militants for their execution.

Although Kassig’s video is accompanied by a clear message to those opposing the Islamic State, this message is not recited by Kassig himself, unlike the other four victims. Nor, unlike the other videos, is the beheading shown -- with only Kassig’s head appearing at the end of the video at the feet of the executioner.

Further, whilst all other beheadings were shot with multiple cameras, Kassig’s execution is shot by only one camera in bad lighting. The video, additionally, is 16 minutes long -- much longer than the other videos that are a few minutes in duration.

Analysts believe that the reason for this key difference could be because the militants -- under increasing surveillance and strikes by western coalition forces -- simply had less time to film the execution.

That said, there are similarities between the latest video and the others. Kassig’s execution is carried out by a militant who has come to be known as “Jihadi John” -- named so for his marked British accent. US intelligence services say that they now know the masked executioner’s identity though he has not as yet been caught. There have however been rumours that “Jihadi John” was wounded in a strike that targeted one of the group’s convoys ten days ago. The US, whilst acknowledging the reports, has not provided any confirmation.

"This is Peter Edward Kassig, a US citizen of your country," Jihadi John says in the video, adding "Here we are burying the first American crusader in Dabiq, eagerly waiting for the remainder of your armies to arrive.”

Although the execution is badly shot, the rest of the video fits in line with the Islamic State’s slick signature production style. The video, before moving to Kassig’s death, shows the gruesome execution of 18 men described as Syrian military personnel. The men, dressed in blue jumpsuits, are led by the scruff of their neck by militants into what appears an olive grove, where each fighter forces his prisoner to the ground and saws through their necks with serrated daggers. The scene is accompanied by slow-motion moments and the added sound effects -- of steel on steel, pounding hearts, and fast breathing -- as the captured men are murdered.

US President Obama, on Sunday, confirmed Kassig’s death. In a statement, Obama said, “Today we offer our prayers and condolences to the parents and family of Abdul-Rahman Kassig, also known to us as Peter,” adding that Kassig -- who was captured at a checkpoint in northern Syria whilst delivering medical supplies over a year ago -- “was taken from us in an act of pure evil by a terrorist group.” Obama’s statement purposely uses the Muslim name Kassig adopted after his capture.

The latest execution comes as President Obama prepares to send more troops to Iraq, having announced a “new phase” in the fight against the Islamic State.