Not to defend what the police have been doing overall during this protest, but in this specific incident you can see the protestors beating a police officer on the ground, and the protestor who got shot was swinging a metal pipe at the police officer that shot him.
The police are allowed to shoot someone in the leg. Lethal force is not the only option with a firearm.
Different police units are trained for different rules. Somewhere it is a verbal warning, warning shot, shot in the leg, shot to kill. Sometimes it is just a verbal warning and a shot to kill. Not defending the police in this specific case (I do not know the details), but blaming an officer for following the sequence he has been trained for is misplacing the blame. My 2c.