An elderly couple who died after their car into a lake may have hit the water because the driver accidentally hit the reverse pedal.
Witnesses claim they saw the male driver looking 'hesitant' in the seconds before the tragedy at Hooe Lake in Plymouth - and believe he was simply trying to find somewhere to park.
The car was then seen reversing before slipping into the lake. The couple, who have not yet been identified, were dragged out of the water by locals and given CPR, but later died at Derriford hospital.
Police were called after reports at 1.55pm that the car had left the road and entered the lake.
The first man on the scene was former police officer Steve Kendall, who drove past the silver Peugeot estate moments before it plunged into the lake.
Mr Kendall said he didn't see the car enter the water - but said he did notice it 'hesitating' on Barton Road.
He said: 'I was driving back to our office on Barton Road directly behind the Peugeot Estate.
'It seemed to hesitate as it was driving towards the quay as if it was going to park. It was like an old person was driving it, who maybe wasn't sure where they were going.
'I drove past and was then flagged down by two dog walkers, who were pointing frantically at the lake.
'I turned around and I could see it on the water. It was upside down floating and then it sank. It all happened in just a few seconds.'
Other witnesses described the vehicle reversing before flipping over raising the prospect that the driver accidentally pushed the accelerator instead of the brake causing the car to reverse and then lose control.
Devon and Cornwall Police said it was too early to speculate on the cause of the tragedy, but said that all lines of inquiry remained open and they were continuing to appeal for witnesses.
Meanwhile, further details of the heroic rescue attempts have emerged and Steve said he was recommending the unknown hero for a bravery award.
As he called the emergency services a second unknown man was already stripped to the waist and swam to the submerged car in an attempt to free the trapped people.
The unnamed hero, who was joined in the water by a police officer, used a hammer Steve provided to smash the car windows and pull the male driver from the wreck.
Mr Kendall said: 'It's supernatural what that member of the public did.
'I contemplated going in but I had already called 999 and you learn when you're in the police that the first person at the scene reports back - you don't jump in.
'It was incredibly brave and he gave it his all but unfortunately, he couldn't save them.
'He deserves recognition for what he did, and so does the officer. I'm going to be recommending the police officer for some sort of commendation.
'They were incredibly brave.'
One witness tweeted: 'Thinking of the family concerned.'
Eyewitness John Wheeler, who came across the scene shortly after the accident happened, said he could see several four or five people in the water trying to help.
He said they could not even see the car initially as it was submerged.
The areas have been completely shut to traffic and police are not letting locals near to the scene.
Locals have previously called for improved safety measures and for steps to be installed where the incident has happened.
One man who lives in the Turnchapel area warned the current layout was 'an accident waiting to happen'.