This per the Washington Examiner.

Capitol Police Officer Brian Sicknick, whose death was initially believed to be caused by rioters during the Jan. 6 insurrection, succumbed to natural causes stemming from a stroke the day after the violence, according to the top medical examiner in the nation’s capital.

Francisco J. Diaz, the chief medical examiner for Washington, D.C., told the Washington Post that Sicknick died on Jan. 7 after suffering two strokes and he did not suffer an allergic reaction to any chemical irritants.