Police officers would have been in great risk if they had tried to stop the rioters, Deputy Assistant Commissioner (DAC) David Scott Arul told the Committee of Inquiry on Wednesday.
When DAC Lu Yeow Lim testified on Tuesday, he highlighted such a scenario.
He recounted that Deputy Superintendent (DSP) Julius Lim, the head of operations and training of E Division, and another officer had tried to arrest a foreign worker who was smashing the window of a police car.
But when a nearby crowd of what seemed like passive onlookers saw what was happening, they came forward and started pelting the officers with bricks and bottles, said DAC Lu.
"This is where you think that because they are passive and they are just standing aside for you come in... that means that they are not rioters.
"This is a fundamental mistake. This is an insurgency," he said.
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