Hundreds of patrons rushed from the Orpheum Theater in San Francisco after hearing shouts of "gun".
A representative for the San Francisco Police Department told EW it appeared the triggered alarm coincided with the sounds of gunfire from the production, at which point the audience began "self-evacuating".
An audience member allegedly suffered a medical event at the same time fake gun shots went off on stage. "People were actively exiting the theater, jumping into police cars thinking there was an active shooter".
However, it is believed that one of the audience suffered a heart attack which caused confusion when an emergency alarm was triggered. One person suffered a broken leg, according to the San Francisco Fire Department, while two other people suffered "moderate" injuries.
SHN added that audience members who attended Friday night's performance are "in the process of being contacted to return to see Hamilton at the Orpheum".
Videos posted on social media showed the extent of the chaos and confusion that occurred at the performance. The theater tweeted the audience and cast followed the life/safety system's automatic announcement and exited the theater.
Laura Lasnier was there with her two children, ages 6 and 9.