Was the Swedish Eriksson twins incident in the UK a case of Folie a deux?

Was the 2008 Swedish Eriksson twins incident in the UK a case of Folie a deux? The case of the 'twisted twins' in 2008 is one of the most chilling and bizarre incidents to have ever been captured on camera in Britain, and it sparked a chain of events that led to the brutal killing of a former RAF airman.