Footage showed a police officer drawing his sidearm in the district of Sai Wan Ho as he tried to detain a masked man at a road junction that had been blocked by protesters.
Another masked man then approached the officer and was apparently shot in the chest area, quickly falling to the ground, clutching his left side. His condition was not clear.
Seconds later, two more live rounds were fired by the officer during a scuffle and another masked man went to the ground, although the footage was less clear as to whether he was struck.
Police could later be seen detaining the two men on the ground. The first man had a pool of blood next to him, his body limp as officers moved him around and apparently tried to tie his hands.