A Barrel of Cooking Oil

"Mr. Zhang, please have some confidence with the police force!" Inspector Loong holds his wrist as he stops Zhang Qin Feng from leaving the police station without an escort. But it was pointless as Zhang Qin Feng left his department without looking back.

The last sentence from the terrorist has already hinted that they knew that Zhang Qin Feng was with the police while they're speaking on the phone.

For them to be this confident even after knowing that their words were monitored by the DongCheng Internal Security means the Horus Eye Mercenaries were a step ahead.

This was what worries the Inspector the most. Zhang Qin Feng shouldn't be in the Police Department's registration because he had him coming straight up to the third floor upon arrival.

If in that case, then from where, and which channel did the people from Horus Eye Mercenaries found out about Zhang Qin Feng's arrival at the Southern District's Police Station?