More than a hundred spectators at the Singapore Sports Hub collapse in their seats as smoke fills the air.
Some lie on the ground, twitching and foaming at the mouth.
Others are wheezing in the stands, gasping for breath.
This was the scene there last Friday night following a mock terrorist attack.
It was part of a rehearsal by the Singapore Civil Defence Force (SCDF) as they prepare for a major emergency exercise next month.
Colonel Francis Ng, the director of SCDF's Hazmat Department, said the scenario was modelled after actual terrorist attacks involving chemical agents.
He said: "By modelling after real events, we are better able to prepare for situations that might happen."
The scene was set in preparation for Exercise Northstar 9, on May 9.
It started with two car explosions outside the Sports Hub, followed by terrorists running to the stands and releasing a chemical agent.
As the casualties fell by the dozen, personnel from SCDF's Hazmat unit rushed in to save them.
Jumping off Hazmat (hazardous materials) buggies wearing their Chemical Agent Suits, they worked quickly to evacuate the casualties.
Meanwhile, a team wearing the Hazmat High Performance Suits, which lets them work with chemicals safely, collected samples of the unknown chemical agent and isolated it.
Personnel were also deployed from the Hazmat Control Vehicle on Mobile Transporters, which allows the collection of samples and the detection of dangerous substances in the air.
Within minutes, casualties were fitted with a Casualty Lifting Kit, which is a headpiece attached to an air filter, and evacuated on stretchers to a decontamination facility outside.
About 80 rescuers were involved, with another 150 SCDF personnel who acted as casualties.
When asked why the Sports Hub was chosen as the location for the exercise, Colonel Ng said it was a new venue and the SCDF wanted to familiarise itself with it, in the event of any emergency.
The Hazmat scenario will be one of the main scenarios that will play out during Exercise Northstar 9.
Colonel Ng said such exercises help prepare responders from the various agencies as well as members of the public to be ready for any emergency here.
"It may just be a mock scenario now, but the threat is very real," he said.
"Threats of terrorism cannot be taken lightly, and such exercises are necessary to help us prepare for any situations that might arise in future."