A private training company sparked an armed police response by carrying out a "kidnapping training scenario" in a town centre without notifying police.
Essex Police said a member of the public saw a woman being pulled from a vehicle at gunpoint in Waltham Abbey and dialled 999. The caller said the vehicle was then stolen.
All available officers in the area were called to respond, along with five double-crewed armed response vehicles and a police helicopter.
The incident was reported to police at around 3pm on Tuesday, and officers carried out stop checks of vehicles matching the description of the one reported as stolen.
"After some time the persons involved were located and it turned out to be a private training company carrying out a kidnapping training scenario in a public place," Essex Police said, writing on the Brentwood and Epping Forest Community Policing Team's Twitter account.
"Police had been given no notification that this would be occurring and the persons involved did not believe this may have been necessary."
The force said the incident has been recorded as a public order offence due to the "alarm and distress that this caused to the members of the public who believed that they were witnessing an incident of violence involving the use of a firearm".
An Essex Police spokesman did not comment on whether further action is being taken.