I believe Mad Mark has hit the mark.
The USCG have a specialist sniper unit that trains to perform exactly what happened here. To take out the engine of a fast mover from a helicopter. Despite what you see in the movies such action is incredibly difficult and carries risks not only to the occupants of the boat but also the aircraft.
Whilst it is possible the RN have copied such a technique, the training and maintenance of such a skill is expensive and I would doubt that the crew of a RN ship be it a bootie or matelot that is only on station for a matter of months have the resources or backing to develop it.
These days it is common if not normal for the West Indies Guard ship or whatever name we now call it to carry onboard a detachment from the USCG so that in the event of such finds they can be dealt with by american authorities from the off. It would therefore be likely that part of that detachment would include an element from their sniper unit.
That being said, a vital part of a successful snipe is the correct positioning of the aircraft to give the man with the gun the best possible chance. For that the RN aircrew should be congratulated. Overall it was a job well done and congrats to all involved, from whatever service or country they originate.
