Matapiro resident Alison Arthur was feeding her four horses when she saw the aircraft, heading east, appear to stall before hearing a loud "bang" as the plane plummeted towards the Ngaruroro River.
She told Hawke's Bay Today the aircraft's movements just moments before the crash looked like "stunt manoeuvres".
"We see planes come up the river all the time, but I first noticed these pop sounds before I spotted the plane. It was way too low. I've never seen one that low around here before, then it started swerving from side to side before it tilted heavily."
Hawke's Bay and East Coast Aero Club president Bruce Govenlock said the deaths of his friend and a UK pilot were a "terrible tragedy".
He said an emergency locator signal, which is activated after an accident, notified the club of the downed Tomahawk PA38 about 11am before emergency services were called and another club aircraft, already airborne, was sent to the location of the signal where the wreckage was found.
"It was not many minutes from the last radio transfer that we noticed the beacon.
"It doesn't appear there was any chance for a distress call and the last radio transmission indicated there was nothing wrong."
He said the two men killed were an "experienced" club instructor and a UK visitor preparing for his pilot's licence validation exam today.
The "fully qualified" UK pilot had been flying the ill-fated two-seater, single-engine plane for about 30 minutes, of the scheduled one-hour flight, after taking off from Bridge Pa Aerodrome.
Mr Govenlock understood the weather to be fine for flying and said it was too early to speculate on whether mechanical or engine failure had caused the 30-year-old, "well-maintained" aircraft to crash.
He said the plane was "well used" for pilot training and the UK pilot had approached the club a couple of days ago to "brush up" on his skills. It is understood he was seeking work for a commercial airline.
"We will be working with all our club members to offer them support as they are all quite shocked," Mr Govenlock said. "We all know the local instructor ... aviation is a tight community and for him to suffer what he has suffered [yesterday] it is very tough."
Club members visited the home of the local man after the crash.
Lowe Corporation Rescue Helicopter pilot Jeremy Bruce was first to arrive at the crash site and saw the plane with its nose down and tail up in the air.
"We managed to land about 10 to 15 metres from the wreckage.
"It was largely intact and virtually in the middle of the riverbed. A paramedic rushed over and discovered both the men in the plane were deceased."
Mr Bruce said flying conditions could be quite different when comparing a helicopter to a fixed-wing aircraft, but said there was little wind and some thick high cloud yesterday.
Crownthorpe farmer Jed Kommeren said he helped emergency services across his family property to the crash site, unaware of the tragedy until police arrived looking for ways to the remote scene.
"My wife had heard it go over low [yesterday] morning, but we didn't really take any notice."
When police and the Fire Service arrived, about 11.45am, he had led them 2-3km across the narrow tracks, as far as the vehicles could go before being confronted by dense willow and other riverbank growth still concealing the crashed plane a few hundred metres away.
The crews made the rest of the trip on foot or were ferried in by Mr Kommeren on his quad bike, to where the wrecked aircraft rested almost in the metre-deep but rushing main stream of the river.
The bodies were still in the wreckage four hours later.
Police said last night the wreck had since been removed from the riverbed.
A Civil Aviation Authority investigation has been launched into the crash.
