Quote :
I thought I had learned the Cantonese word for "police", because that was what I heard everyone, including little kids and tiny elderly grandmothers, call out when they saw riot cops coming. It turns out I had learned the Cantonese word for "dog".
— Pinboard (@Pinboard) September 9, 2019
They would yell 警察/阿sir/差佬 => Police, 黑警 => ‘Black’ police, 黑社會 => Triad, 狗 => dog. And some finer categories: 速龍 => raptor team, 防暴/綠衫 => riot police, 藍衫/白衫 => blue/white shirt officer.