First...Prayers and sympathy for All invovled with this tragic accident.
Flying Magazine said in an unrelated story:The above is speculation, thought of the above and the story on a coast guard rescue copter crash in Flying. To be short I agree with Tanks posting(s) on the subject.Helicopters are susceptible to potentially disastrous vortex ring effects. In these, the downward wind from the rotor causes a circular vortex to form around the rotor. If this ring is augmented by terrain, wind, rain, or sea spray, the helicopter can lose enough lift to experience settling with power and hit the ground.