After yet another American aid worker is beheaded by the Islamic State in Syria, experts believe that the next victim will be a woman.

Peter Kassig, the 26-year-old aid worker who was first threatened by ISIS after October's beheading video of British humanitarian Alan Henning, was the latest victim of the Islamic terrorist group. His video was released on Monday, but it raised some concerns by experts who have been studying the patterns of each beheading video released.

While the one speaking in the video is said to be the same man as in the other videos, an ISIS member only known as "Jihadist John," the circumstances of the video and its usual set-up were different.

In previous videos, the masked executioner showed the actual beheading act done on each victim, with the next victims lined up on the side. This formula worked with American journalists James Foley and Steven Sotloff, as well as British aid workers David Haines and Alan Henning. This video, however, simply showed a severed head at the feet of the video's speaker, with no one else visible in the shot.

Some are saying that this is for several reasons. Speculation from Kassig's former roommate suggests that the former U.S. Army Ranger fought his captors at the end. "Clearly something went wrong," noted Mitchell Prothero, Kassig's roommate in Beirut. "My belief is that he knew it was up and did something to screw up their video. There's no way they planned for 14 minutes of them killing Syrian guys and then 30 seconds at the end of them killing Pete."

But the absence of other potential victims in the video also has some experts concerned. The last American currently being held captive is a female aid worker who was captured in Syria last year. While her name is not being released out of respect to her family, her beheading would mark the first time ISIS has captured the beheading of a Western woman on video. The terrorist group does not specifically name the woman as the next victim, but her status as the last American captive leads experts to believe that she was being saved to make a greater statement. Her ransom is currently set at $6.6 million.

These beheading videos are in response to the terrorist group's concern over western presence in Syria and Iraq. The Islamic group threatens to continue with the slaughter of not only American and British aid workers taken captive, but also more Syrian rebels, and even U.S. military personnel.

"We say to you, Obama...you claim to have withdrawn from Iraq four years ago," the speaker in the video said. "Here you are: you have not withdrawn. Rather, you hid some of your forces behind your proxies. Here we are, burying the first American crusader in Dabiq, eagerly waiting for the remainder of your armies to arrive."

"Today we are slaughtering the soldiers of Bashar," the speaker continues. "And tomorrow we will be slaughtering your soldiers and with Allah's permission we will break this final and last crusade and the Islamic State will soon, like your puppet David Cameron said, begin to slaughter your people on your streets. "

The U.S. launched air strikes earlier this year to combat the remnants of al Qaeda that regrouped to form the Islamic State in Iraq and Syria (ISIS). In June, the group captured almost a third of Iraq and much of Syria in hopes to establish an Islamic caliphate. It is estimated that ISIS has so far collected over $125 million through ransom payments, mostly from European countries.