Sister's shock over claims her brother and ex-bouncy castle salesman is the new Jihadi John

The sister of an ISIS fanatic accused of being the masked executioner dubbed the 'new Jihadi John' says she will 'kill him myself' if it is confirmed to be him. British security agents are racing to identify the militant who spoke with an English accent in a sick new execution video in which he is seen shooting an alleged British spy (right). Speculation mounted today that the gunman could be Siddhartha Dhar, a British jihadi who fled to join the terror group in Syria while on police bail for

encouraging terrorism in 2014 (pictured centre at a rally). The former bouncy castle salesman posted a picture of himself cradling his baby while brandishing an AK-47 to taunt security services whose blunders allowed him to escape (inset). His sister, Konika Dhar, (left) admitted the voice sounded 'a bit like' her brother. Ms Dhar, from North London , said: 'If it is him, bloody hell am I shocked. I am going to kill him myself. He is going to come back and I am going to kill him if he has done this.'