Not only did he slaughter nobles and betray the Kingdom, but he also colluded with Evil Spirits.
"Do you not fear the pyre of the Religious Tribunal?!"
The incident of murder by Evil Spirits on Melrose Street was, in fact, utterly ordinary. The only exceptions were its proximity to the Royal Palace, the unusually high-profile victims, and the rather unsightly manner of their deaths. It was never even reported to Edward IV, so as not to spoil his good mood. Even if it were eventually reported, such a report would have to wait until the cause of the incident was investigated and a response plan formulated.
"Covering up" such matters was purely the instinct of old bureaucrats and didn't depend on the world in which they operated.
