a Pilot flys over a known heli park
Which chart is this 'known' heli park shown on ??? Can't find it on my Half Mil. Unfortunately in Class G airspace without an ATZ you have no God given right to protection from any other airspace user. It's 'see and be seen' for all parties. In this case you saw the other aircraft and thus did not collide with it. Another success for this not 100% fail safe system.
To be legal, the fixed wing pilot would only have to maintain 500' separation (vertical, horizontal, or combination of both) from any person, structure, etc. Thus as Zlin stated, it is quite possible that the pilot was operating totally legally.
It may also have been a military aircraft flying a low flying training profile (Grob Tutor for example), in which case other low flying rules come in to force. The ANO also exempts military aircraft.
If you are really that concerned then why not file an Airprox report ?? It would investigate all the issues and bring lessons to everyone.