LONDON, Jan. 6 (UPI) -- The suspected Islamic State executioner recently seen in a video that purports to show the killing of five hostages has been identified by media outlets as Siddhartha Dhar, a British Indian who converted to Islam.
Dhar, 32, also known as Abu Rumaysah, fled Britain two days after he was released on bail in September 2014 on charges of allegedly encouraging terrorism. He was a well-known figure among London's radical Islamists.
He was banned from traveling and ordered to hand over his passport to police. However, BBC News reported he boarded a vehicle from London's Victoria Station toward Paris along with his family.
Dhar, who was previously a Sikh and inflatable castle salesman, later posted an image of himself holding a rifle and his newborn child -- his fourth -- on Twitter as he announced his arrival in Syria.
"What a shoddy security system Britain must have to allow me to breeze through Europe to [Islamic State]," Dhar then tweeted. He previously led the al-Muhajiroun network, a group banned under Britain's terrorism legislation.
Konika Dhar, his sister, said she fears the masked murdered could be her brother, but said she is not "entirely convinced" it is him. In an interview with Sky News, she said the executioner may not be Dhar because the man in the video does not sport pronounced eyebrows like her brother.
"I was in a state of shock," she told BBC. "I believed the audio to resemble, from what I remember, the voice of my brother but having viewed the short clip in detail, I wasn't entirely convinced which put me at ease."
In the 11-minute film released by the Al-Hayat Media Center, the Islamic State's media wing, an unidentified masked militant -- believed by some to be Dhar -- threatens attacks on Britain, specifically sending a "message" to British Prime Minister David Cameron.
"Oh slave of the White House, oh mule of the Jews. How strange it is that we find ourselves today hearing an insignificant leader like you challenge the might of the Islamic State," the masked man says. "How strange it is that the leader of a small island threatens us with a handful of planes. One would have thought you would have learned the lessons of your pathetic master in Washington and his failed campaign against Islamic State."
At the end of the video, a young boy dressed in military attire is also seen. He warns in English: "We are going to go kill the kafir [non-believers] over there."
Charlie Winter, a senior researcher in transcultural conflict at Georgia State University in Atlanta told The Guardian that the Islamic State -- also known as Daesh, ISIS and ISIL -- has launched a propaganda campaign in an attempt to distract from mounting losses, particularly after losing control of the Iraqi city of Ramadi.
"Among other things, ISIS is trying to seize the initiative again, having taken a major hit with the loss of Ramadi," Winter said, adding there had been "an uptick in propaganda videos and photo essays" recently, designed to "divert attention away from big tactical blows like Ramadi.