The lead investigator, Howard Plagens, said the pilot of a vintage Hawker Sea Fury TMK 20 pulled up to the left side of a travelling companion flying a Cessna 210. The Sea Fury's pilot heard a "thump" and immediately focused on trying to fly his own plane to land safely.
Plagens said the pilot saw the Cessna going down but did not see it crash.
"Obviously, he's still shaken up," said Plagens, who interviewed the surviving pilot twice.
The effort to find a missing Cessna and its pilot has gone from search and rescue to recovery.
The Contra Costa County Sheriff's Office said searchers located the Cessna under 13 feet of water about 1.5 miles off the Richmond shoreline east of San Francisco shortly after the US Coast Guard officially suspended its search for the plane on Monday afternoon. The pilot hasen't been located, and officials haven't identified the two pilots.
The Harbor Master at the Point San Pablo Yacht Harbor told ABC7 News he has watched the search effort for two days, knowing the conditions were difficult, despite the shallow depth of the water.
"It breaks my heart. I mean there were so many boats on site immediately and I didn't see anybody come up. Debris came up, they actually found his backpack, phone and ID and stuff in it, pulled it out of the water. The arm rest on the door, somebody saw it float up," Eric Johnson said.
The collision occurred at about 4 p.m. Sunday near the Richmond-San Rafael Bridge. The Cessna was apparently flying back with the Hawker Sea Fury TMK 20 to their home base at the Eagle's Nest Airport in the small city of Ione in Amador County when the two collided.
The Sea Fury's occupants - a husband and wife - were uninjured. It was unclear how many people were in the Cessna.
Both planes had departed from Eagle's Nest Airport to participate in the Pacific Coast Dream Machines, an annual festival at Half Moon Bay Airport that features a variety of planes, motorcycles and cars.
FAA records indicate the Hawker Sea Fury TMK 20, a vintage British fighter plane, is registered to Sanders Aeronautics Inc. in Ione. A man who answered the phone at the company's listed number declined to comment.
The Associated Press contributed to this story.