We had a similar event on the EC225 in front of the passenger terminal (aircraft leapt into the air with lots of nose down!). In the case of the 225, the solution is to be sure to lock the collective first, then apply the parking brake.
But IIRC the 76 has no lock nor friction on the collective? If you fly 2-pilot, one possibility is to pass control of the collective to the other pilot before applying the parking brake. Or even mod the aircraft to fit a collective lock?
Whilst we have cars that have handbrakes that resemble collectives, this incident is bound to happen from time to time unless procedures are in place to prevent it. Without adequate procedures (that are adhered to ) its only a matter of time before it happens again.
HC