An English-speaking child, and a British-sounding militant who brings to mind ISIS' previous propagandist, 'Jihadi John,' appear in the latest, chilling propaganda video from ISIS.

In the video, which has not yet been independently verified, the child says that the group will kill "kuffar' -- nonbelievers -- "over there," referring to the West, while the adult threatens and insults British Prime Minister David Cameron.

He calls the Prime Minister a "slave of the White House" and an "imbecile."

"Only an imbecile would dare to anger a people who love death the way that you love your life," he says.

"Know that today, your citizenship is under our feet," the man in the latest video continues, addressing British citizens and pointing his weapon at the camera. "And that our country, the Islamic State, is here to stay, and we will continue to wage jihad, break borders and one day, invade your land, where we will rule by the Sharia."

Islamic State is another name for ISIS, and he refers to Sharia law, a strict interpretation of Islamic law.

After his speech, the five captives, dressed in orange jumpsuits similar to those that ISIS has made previous murdered captives wear, are killed with a gunshot to the back of the head.