Usman Khan was convicted of terrorism-related offences at age 20, and sent to high-security prison. He was released eight years later, and allowed to travel to London for one day, to attend an event marking the fifth anniversary of a prison education programme he participated in. On 29 November, 2019, he sat with others at Fishmongers' Hall, some of whom he knew. Then he went to the bathroom to retrieve the things he had hidden there: a fake bomb vest and two knives, which he taped to his wrists. That day, he killed two people: Saskia Jones and Jack Merritt.