The four-seat Robinson R44 went down in a gated community in Newport Beach, about 45 miles (72 kilometers) southeast of Los Angeles. Four people were on board the helicopter.
The injured were taken to hospitals but there was no immediate word on their condition.
"I was upstairs and all of a sudden the house just shook and I thought, 'Oh my gosh, we're having an earthquake,'" said Marian Michaels, who lives behind the home where the helicopter crashed.
Roger Johnson was doing some woodwork in his garage when he heard the sound of a helicopter and then a tremendous boom across the street.
"I turned to look out of the garage and that's when I see this piece of metal flying through the air and hitting a bush and garage door," Johnson said. "Then I heard someone scream — a real for-real horror scream, like something terrible had happened."
Johnson rushed to the wreckage and several people started to try to pull victims out of the helicopter. That's when Johnson urged them not to move them for fear of further injuring them.
Fire Chief Chip Duncan confirmed the three deaths and injuries but could not say how many of the dead were aboard the aircraft.
A neighbor who heard the crash told KCAL-TV that he saw the pilot lying injured but alive on the grass and three other people inside the wreckage.
"We tried to pry them out but we didn't want to touch them," said the neighbor, who was not identified by the television station. "We didn't want to take a chance of hurting anybody."
"The three people were all crunched in there together," he said. "One I could see moving an arm."
The helicopter crashed into the house with such force that it was barely recognizable. The crushed metal sat in a heap on the side of the house, its tail rotor sticking out of the roof of a nearby home a 6-foot (1.8-meter) chunk lying down the street in front of yet another house.
Audrey Ellis, who lives next door to the house where the crash happened, was not home at the time but said her neighbors told her they were in the kitchen when the helicopter hit the bedroom of their house.
"It's so scary," Ellis said, adding that her neighbors weren't hurt. "I'm so thankful."
The aircraft had taken off from John Wayne Airport, said Ian Gregor, a spokesman with the Federal Aviation Administration. The airport is about a mile (1.6 kilometers) from the crash site. There was no fire.
Messages seeking comment from Revolution Aviation, which is based at the airport and operated the helicopter, were not immediately returned.
The company offers helicopter and airplane classes, the use of aircraft for photography and video production as well as sightseeing flights.
The crash happened two days after a small plane heading toward the airport made a nighttime emergency landing on a nearby freeway. The pilot and passenger weren't hurt.
The pilot, Israel Slod, said the engine of the Beech G33 suddenly died as the plane was en route from San Diego to the airport.
The aircraft landed on State Route 55 in Costa Mesa, a few miles north of Newport Beach.
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