CBS News reported five people, including a child, were hospitalised after the incident, which took place in the city of Huntington Beach around 2pm on Saturday local time (10am Sunday NZT).
City officials told the outlet that two occupants of the helicopter were safely pulled from the wreckage, while three pedestrians were also injured in the crash.
All were hospitalised in an unknown condition.
An aerial view from the outlet showed debris from the chopper scattered across the beach access carpark.
It also showed that the tail of the helicopter had broken off in the crash.
Accident witness Kevin Bullat told CBS News, “You can hear this odd sound that didn’t sound right”.
“I looked out and I see the helicopter spiralling out of control. ... My friend saw shrapnel, or just debris, catapulting across PCH [Pacific Coast Highway].”
According to the outlet, a helicopter landing party was being hosted nearby to where the accident took place.