More sinister theories claim he was assassinated: One is that the killer was a Swedish compatriot and asserts that enemy guns were not firing at the time Charles was struck. Suspects in this claim range from a nearby soldier tired of the siege and wanting to put an end to the war, to an assassin hired by Charles's own brother-in-law, who profited from the event by subsequently taking the throne himself as Frederick I of Sweden, that person being Frederick's aide-de-camp, André Sicre. Sicre confessed during what was claimed to be a state of delirium brought on by fever but later recanted. It has also been suspected that a plot to kill Charles may have been put in place by a group of wealthy Swedes who would benefit from the blocking of a 17% wealth tax that Charles intended to introduce. In the Varberg Fortress museum there is a display with a lead filled brass button - Swedish - that is claimed by some to be the projectile that killed the king.