My understanding is that lots of rookies are sent in there - that if they can hack a patrol in the South Bronx they can deal with any other standard assignment, and that the ones who distinguish themselves can be identified for more specialized assignments.
That may be a good idea, dependent on how many mistakes are made. Not that this was one; I believe this officer proved he has what it takes though there will certainly be tough times for him ahead, both in dealing with having taken a human life and in dealing with the charges of murder from uninformed family members and others who are without clue one.