The reason why people are saying, "You killed our Commissioner General"

This is exactly what "You killed our Commissioner General" means.
If you act as an informant after setting the stage, this is how you die.
Then that Commissioner kept insisting, "This kid caused trouble," right? This is how someone dies while doing that.
This is why having a setup prepared is so terrifying.
The Security Chief at the Seoul Metropolitan Police Agency was making a huge scene, trying to protect his subordinate by claiming, "It's illegal filming," right? It was total chaos.
That is what happened. He got completely destroyed by treating the kid like that.
And this kid managed to endure it all.