SAN FRANCISCO, CA. (THECOUNT) — Chaos broke out during a performance of the musical “Hamilton” at San Francisco SHN Orpheum Theatre after audience members mistook a medical emergency for a shooting.

City Fire Department spokesman Jonathan Baxter said a woman had a heart attack during the Friday night performance and someone broke open an emergency defibrillator, activating an alarm as theatrical gunfire went off during the show’s duel scene, reports WTAE.

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Three people were injured as panicked audience members rushed out of the theater. One person broke a leg and two others had moderate injuries.

The woman who had a heart attack remained hospitalized Saturday in critical condition.

A message to theater spokesman Scott Kane hasn’t been returned.

Developing.