Much has also been made of the role of rumours circulating on social media about this incident, and the singer songwriter Olly Murs got into a public spat with Piers Morgan after tweeting to his 7.83 million followers on Twitter that there had been gunshots in Selfridges. I would certainly advocate that the information disseminated in emergencies should be as accurate as possible, and that people with large numbers of followers on social media need to be careful with what they put in the public domain. However, I feel that it is a little unfair when people external to the event criticize those caught up in it for spreading inaccurate information, as they may have the hindsight that those within in it do not. It is also important to bear in mind that for rumours to spread in such incidents, they still have to be credible to be believed and acted upon by crowd members. One could say in the current context of fear of terrorist attacks in London post Westminster/ London Bridge, Parsons Green etc, that rumours of another attack could be considered a credible threat, especially since the authorities took the incident seriously enough to dispatch armed police to the scene. However, other less credible rumours (e.g. that Godzilla was charging up Oxford Street!) may not have been so readily believed. The crucial thing is for the authorities to be as open & honest as possible with the information they provide, so that people don't feel such a need to seek information about the incident from other sources. A common myth about emergencies is that if people become aware of a possible threat, then they will be come too fearful to act rationally and will therefore 'panic'. However, there is almost no evidence to support this idea, and withholding information in emergencies could even result in people delaying action to keep themselves safe, and so could ironically increase the danger.
Cocking C. (2013) Crowd flight during collective disorder- a momentary lapse of reason? Journal of Investigative Psychology & Offender Profiling,10 (2) p.219-36. DOI:10.1002/jip.1389
Drury, J. and Cocking, C. (2007). The mass psychology of disasters and emergency evacuations: A research report and implications for practice. http://www.sussex.ac.uk/affiliates/panic/Disasters%20and%20emergency%20evacuations%20(2007).pdf
Drury, J., Cocking, C., & Reicher, S. (2009a). Every one for themselves? Understanding how crowd solidarity can arise in an emergency: An interview study of disaster survivors. British Journal of Social Psychology 48.