Lasting for two and a half hour, the exercise simulated a robbery in which two culprits discharged a chemical substance before making good their escape in a getaway car. The substance reportedly affected some civilians gathering at the terminus, and Police Operation "EXIGENT" was activated.

About 100 officers from the Fire Services Department, the Hospital Authority (HA), the Home Affairs Department, the Auxiliary Medical Service, Emergency Unit New Territories North, Tai Po Division and New Territories North Regional Headquarters were mobilised and raced to the scene, personal protective gear. HA deployed a medical team to the scene while firemen equipped with "Hazmat Pod" set up a zone for decontaminating a large number of casualties who were later sent to hospital for further treatment.

According to New Territories North Senior Superintendent (Operations) Yu Mun-wah (now CSP Support), the exercise focused on the emergency response of the units involved in rescue, evacuation and decontamination of mass casualty. He emphasised that the chemical substance used could be readily available in the local market and that such incident might not be perpetrated by terrorists.

"The exercise provided an opportunity for various departments to examine their standing orders relating to incidents of a similar nature, and to test frontline units' mobilisation readiness in this regard," he noted.

Helping a victim at the scene