09:05 EDT, 19 April 2021 Advertisement A witness to the Fishmongers' Hall terror attack which left two dead and three wounded said he initially thought killer Usman Khan was 'play fighting' when he launched his murderous assault, an inquest jury has heard. Convicted terrorist Khan, 28, was armed with two knives and wore a fake suicide vest as he stabbed Cambridge University graduates Jack Merritt, 25, and Saskia Jones, 23, to death and injured three others at a prisoner rehabilitation event near London Bridge on November 29, 2019. The killer, who was let out halfway through his 16-year sentence on licence after pretending that he had been de-radicalised, was tackled by heroic members of the public brandishing a decorative pike, narwhal tusk and fire extinguisher before he was then shot dead by police.