He is most critical to how a riot could turn out.
As such, the decisions made by the incident manager, usually the commander of a police division, are crucial.
A wrong assessment of the situation or deployment of forces could result in greater violence.
That was what Mr Khoo Boon Hui, senior deputy secretary for the Ministry of Home Affairs, told the Committee of Inquiry yesterday.
Mr Khoo, who was the Commissioner of Police between 1997 and 2010, appeared before the Committee yesterday and spoke about the riot control doctrine and measures here.
While he said that dealing with a mob is best left to the trained and equipped troopers from the Special Operations Command (SOC), the incident manager is responsible for managing the situation.
This is what Mr Khoo said the incident manager must do:
1. Assess the situation
What does the crowd want? Is the entire crowd passive or aggressive? Are there ringleaders?
These are questions that the incident manager will need to answer, said Mr Khoo.
It is not an easy role, given the incident manager will also need to give information to the police command, worry about the safety of his officers and decide on the most effective tactics based on available resources.
He is also the one who makes the request for reinforcements, if needed.