The crash initially happened around 1:50 p.m. local time in Newport Beach, NBC Los Angeles reported. The Newport Beach Police Department said four people were aboard the Robinson 44 helicopter when it went down.
One of the deceased was a person who was on the ground when the crash occurred.
A resident in the neighborhood described to local station KCAL-TV what he heard and saw after the crash took place.
"We tried to pry them out but we didn't want to touch them," the neighbor told the station. "We didn't want to take a chance of hurting anybody."
"The three people were all crunched in there together. One I could see moving an arm," he added.
The crash site is roughly a mile away from the John Wayne Airport in Orange County, according to CBS News. A witness told the outlet that he saw the helicopter "drop like a rock."
According to reports, no fire has erupted despite fluids building up on the ground.
The cause of the crash is currently under investigation and will be handled by the Federal Aviation Administration and the National Transportation Safety Board.