Five armed response vehicles rushed to Long Lane on Friday night after local residents reported gunshots and screams.
The source of the noise was an empty office building being used by COLAB Theatre for a 'pervasive theatre' show called Hunted.
Borough Police tweeted on Saturday morning: "Attended a call to gunshots / people screaming in Long Lane #SE1 last night. 5 ARVs attended. Turned out to be a show by @CoLab_Theatre.
"Local residents had been informed about their shows but one hadn't read the letter. Local police had no idea!"