Another article says the boy, in the case in question, was taken to hospital with serious head injuries but released later the same day after treatment. I think that contradicts itself. You're usually kept in, under observation, for a just a bad bump. So was it serious or not.
To me this is a worrying bit of the IOPC's statement, "Ultimately no police tactic can ever be used with impunity in a country where we police by consent - be that tactical contact, the use of firearms or the use of restraint."
If i was a policeman i would be starting to worry what action i could taken in stopping a crime and would i be liable for prosecution for my action.