Of course, not all the details are given in that short story, so we cant play armchair general and say whether the approach was right or not; unless you know more of the story you cant just blindly approve or disapprove of the action taken.
Knowing only the facts in the story, I would disagree with your comment; there needs to be something besides just a 'report' to justify slamming a persons face into the ground and kneeling on them, i.e. they look like gangbangers, they're holding weapons, they're threatening to kill people, acting intimidating, resisting arrest, etcetera...