Multiple witnesses living near the accident site reported observing portions of the accident sequence.
One witness, who was walking on a levee near the crash site, said she saw an airplane "suddenly appear from the fog" to her left. She said she continued to watch the airplane fly from her left to her right at a low altitude until it hit power lines, according to the report.
Parts of the Cessna, piloted by Doug Bourn, a senior electrical engineer with Tesla Motors, crashed into several homes and the ground following the collision with the power lines and tower, the report noted.
Bourn, a licensed commercial pilot, and his two passengers, Andrew Ingram and Brian Finn, also Tesla employees, were flying to Hawthorne, Calif., for a meeting. All three men were killed. The airplane was registered to Air Unique, Inc., of Santa Clara, and piloted by Bourn as a personal flight.
"Instrument meteorological conditions prevailed and an instrument flight plan was filed for the cross-country flight," the NTSB report said.
"Examination of the accident site revealed that the airplane struck power lines and a power line tower about 50 feet above ground level. Various portions of wreckage debris, power lines, and power-line tower structure were scattered throughout the wreckage debris path," according to the report.
The southwesterly debris path measured approximately 900 feet from the tower and wires to where the main fuselage of the plane came to rest in front of a residence on Beech Street. In total, a post-crash fire and wreckage debris damaged four homes and at least five vehicles.
All major structural parts of the airplane were located and are being studied by NTSB investigators. A fuel-laden wing, believed to have been severed by hitting the power lines or tower, crashed into a home housing a day care center and burst into flames, but all of the seven persons there escaped unhurt.
The plane's engine, landing gear and part of the fuselage destroyed a carport and the car in it, and the engine continued on, smashing the side of a garage and winding up inside the garage.
Joshua Cawthra, the NTSB lead aviation accident investigator, said a final report to determine the exact cause of the crash would take six months to a year.
"The process is very time consuming. It depends on where the investigation leads us. If it's mechanical failure we have to dig deeper as to why there was a failure," he said.
Cawthra said whether the plane impacted with the tower or wires first isn't known at this point.
"We may never know. It was pretty instantaneous," he said.
No flight recorder was required on the plane and the airport control tower did not receive any distress calls prior to the crash, Cawthra said. Investigators are examining five audio recordings of the crash picked up by East Palo Alto Police Department's ShotSpotter gun-shot detection system, however.
The recordings picked up 11 seconds of the accident, which included the sound of the plane's engines just prior to the crash, the impact into the wires and tower and subsequent impacts with homes and the street, according to police. It is the first time in aviation history that such a recording will be used for forensic purposes, Cawthra said.
ShotSpotter filters sounds to separate gun shots from other noise and then reports the gunfire and location to police. The system automatically classified the crash as loud and impulsive but not gunfire and did not report the incident in real time to the East Palo Alto Police dispatch. But company employees realized the information was cached after learning of the crash and provided the audio recording to police, said James Bedlock, company president.
Memorial services for the three men are pending. Finn is to be eulogized in DeKalb Area Retirement Center Oakcrest Chapel in DeKalb, Ill., and a memorial service is planned for Bourn on Feb. 27. Ingram's family said they plan to hold a memorial service sometime this summer.
To honor the three victims, East Palo Alto residents on Beech Street built a small shrine at the crash site out of bricks and plywood and adorned it with flowers, candles, stuffed animals and several fragments of the plane.