INDIANAPOLIS -- The cause of death of an Indianapolis oral surgeon who piloted a small plane that crashed into a local pond this week could be known Wednesday, a Marion County deputy coroner said.

Preliminary results of Tuesday's autopsy of Dr. Robert Edesess were inconclusive, but further examination was expected to lead to the cause of death, the deputy coroner said.

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Video: Coroner: Cause Of Pilot's Death Could Be Known Wednesday

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Authorities said Edesess was piloting a small plane carrying three other people when it took off from Eagle Creek Airport on Monday morning. Shortly after takeoff, a parachute deployed behind the aircraft, slowing the plane as it fell into a retention pond in a subdivision near 21st Street and Raceway Road.

Bystanders went into the pond and pulled Edesess and the three passengers -- his wife, one of his son's and the son's girlfriend -- out of the water. Edesess died later Monday at Methodist Hospital, where the other three -- Poulfiri Edesses, Jeremy Edesess and Janet Adams -- were in serious condition Tuesday morning, officials said.

One of Robert Edesess' friends, Chuck Huff, told 6News' Jeremy Brilliant that Methodist medical personnel said Edesess suffered a medical emergency during the flight and became unable to pilot the plane.

"I know that he had ... a brain hemorrhage and he became incapacitated," Huff said.

The deputy coroner told 6News that she was looking into this explanation, but she had not drawn any conclusions by Tuesday afternoon.

Huff said he spoke to Jeremy Edesess, who he said activated the plane's parachute. The parachute is designed to slow the plane in an emergency.

"When Jeremy said, 'If it hadn't been for the parachute, we'd be done,' I told him his dad would be proud," Huff said.

The plane avoided several nearby homes when it crashed into the pond.

Witnesses said Robert Edesess wasn't breathing when he was pulled from the water, and that someone resuscitated him before he was transported to Methodist. It appeared that something had hit him in the head, witnesses said.

Edesess intended to fly the plane to Hilton Head Island, S.C. He had just bought the plane, which federal records showed was made this year and was airworthy before the crash, 6News reported.

A federal investigation into the crash could take months, 6News reported.