Whirlygig
Other witnesses report they heard "the engine stall" - it was a twin.
Someone else said "I looked up and saw the helicopter falling down nose-first with the rotor blades off. It was not on fire at that point and the blades were trailing 10-15ft behind."
Witness reports from members of the public, just like their estimates of height in other circumstances, always have to be treated with great caution.