The image was intercepted by a intelligence firm Black Ops Cyber, reports The Epoch Times.
However, police later confirmed there were no gunshots or suspects – and the only injuries were people hurt the crush.
Streets are expected to heaving in London over Christmas with Britain remaining under a “severe” terror alert – meaning an attack is highly likely.
UK TERROR ALERT: Police stage huge mock mass shooting exercise known as " Exercise Strong Tower " Members of the public and emergency services take part in a mocked-up shooting.
Could this be what it would be like if a real terrorist firearms attack happened in central London.