Jim King was golfing at the course right next to the airport when the plane went down around 4 p.m. Sunday. "It picked up power, it stalled and we all looked at each other in the eye and was (sic) like that doesn't sound right," he said.
RELATED: Officials confirm 2 killed in small plane crash near Petaluma Airport
King and his friends are used to seeing planes take off from the airport and knew immediately something was wrong. "Finally, just sounded like it stalled completely and spiraled down and onto the roadway," he said.
"Played with a couple of firefighters today," explained Tom Graham, who was also on the golf course when the plane crashed. He said the firefighters, "rushed over. I didn't quite go over there, and they came back and blessed themselves and said they're dead."
Police say a man and a woman were on board the plane and that both of them were killed in the crash.
A tow truck w/crane arrived to clear plane debris. A man and woman were killed when their "amateur built custom manufactured" plane crashed pic.twitter.com/g24ZGcQt09— Kate Larsen (@KateABC7) May 28, 2018
According to an NTSB investigator on scene, the aircraft, a Vans RV6, was an "amateur built custom manufactured plane" that had been in service for quite some time.
"At this point in time, we don't know the cause of the accident," said Lt. Brian Miller with the Petaluma Police Department, who added, "It's our understanding that it was taking off and it may have attempted to return to the airport."
Late Sunday night, a flat bed truck and crane arrived to clear the plane debris off East Washington Street.
The NTSB and the FAA are investigating the crash. The plane is registered to an address in American Canyon.
Two people killed in this plane that crashed on a road 1000 yards from Petaluma Airport. FAA and NTSB are investigating the cause. pic.twitter.com/3LJEqFoV5H— Kate Larsen (@KateABC7) May 28, 2018