In this case it had occurred complicating sepsis.
[endocrine-abstracts.org]
[…] distinguishing factors rarely the extreme tachycardia seen in thyroid storm thyroid functioning tests will likely be normal in sepsis Treatment Management approach management
[medbullets.com]
[…] common cause of death in TS1 and TS2, followed by CHF, respiratory failure, arrhythmia, disseminated intravascular coagulation, GI perforation, hypoxic brain syndrome, and sepsis
[ncbi.nlm.nih.gov]