It started out as a normal Wednesday morning train journey for the nine people on board the 6.30am Aberdeen-Glasgow service.
But heavy rain the previous night had left the track in treacherous condition.
Having failed to get much further than Stonehaven, the ScotRail service turned back – but only as far as a landslip, which sent it careering down an embankment.
Some of the carriages came to a halt upside down and three people – the driver, conductor and a passenger – lost their lives.
Here’s a full recap of how events unfolded on that morning and since.
The five-carriage ScotRail train departed from Aberdeen at 6.38am on Wednesday morning on its way to Glasgow.
After hitting some heavy flooding – due to overnight thunderstorms – on its way down south, the decision was made to head back to Aberdeen.
A short time into the return journey, the train struck a landslip and derailed shortly near Stonehaven.
The leading power car continued over the bridge and then fell from the track down a wooded embankment, as did the third carriage.
The first and second carriages landed on their roofs and the fourth carriage remained upright and attached to the rear power car.
The alarm was raised around 9.38am as plumes of smoke could be seen billowing from the crash site.
Dozens of emergency service vehicles, including an air ambulance, were called to the area.
Three people, the driver, the conductor and a passenger, were pronounced dead at the scene.
A further six people were taken to hospital with minor injuries.
Who were the victims?
Three people died at the scene of the crash. Six others were taken to hospital with injuries and four have since been discharged.
Train driver Brett McCullough, conductor Donald Dinnie and passenger Christopher Stuchbury were killed.
Mr McCullough was a 45-year-old father-of-three originally from Bromley in Kent.
He moved to Aberdeenshire to marry his wife and worked out of the Aberdeen depot.
Conductor Mr Dinnie had a lengthy career on the tracks after also working as a driver and a guard.
The 58-year-old left behind a large group of family and friends.
Mr Stuchbury, who was a passenger on the derailed train, worked for a marine services firm in Aberdeen.
The 62-year-old also volunteered at Roxburghe House hospice in his spare time.
A total of nine people, including the crew, were on board the train during the crash.
Did extreme weather play a part?
The derailment happened after the train hit a landslip following a night of thunderstorms and flooding in the area.
The details emerged on Friday from an ongoing probe by the Rail Accident Investigation Board.
On Thursday, the transport secretary said he believed extreme weather played a part in the crash.
During a visit to Stonehaven, Michael Matheson said: “I think it would be reasonable to presume, without unduly speculating, that weather had an impact in this particular incident.”
He added that adverse weather was increasingly having an impact on routes and a probe would reveal whether more mitigation works were needed.
He said: “I think one of the things we will see what comes from the investigation is whether the pace of that type of mitigation work needs to be stepped up, that’s not just a challenge across Scotland, it’s across the whole of the UK.”
How will it be investigated?
A joint investigation is being carried out by Police Scotland, British Transport Police and the Office of Rail and Road.
They will be under the direction of the Crown Office and Procurator Fiscal Service.
In parallel, an independent safety investigation is being carried out by the Rail Accident Investigation Branch (RAIB).
The branch said it has sent a team of inspectors to the site of a derailment near Stonehaven.
However, railway expert Tony Miles, of Modern Railways Magazine, told STV News a full probe could take “a year or more”.
He said: “Full investigations tend to take up to a year or more because they’ll want to be very careful to make sure that they reach the right conclusions but there might be some very quick lessons learnt from this.”
Timeline of tragedy
6.38am: The Aberdeen to Glasgow Queen Street service departs on time.
6.53am: The service calls at Stonehaven railway station.
7am: The train stops for a landslip between Stonehaven and Carmont railway stations.
9.30am: The train is held up for more than two-and-a-half hours before being moved onto the northbound track to be sent back to Stonehaven.
Shortly after this, the train hit a landslide.
9.38am: A member of the public dials 999 to alert the emergency services.
9.43am: Police Scotland are notified.
11.15am: The multi-agency response – including the Scottish Fire and Rescue Service (SFRS), Scottish Ambulance Service, Scotland’s Charity Air Ambulance and HM Coastguard – are pictured working at the scene.
3.30pm: NHS Grampian sets up a help centre at Midstocket Parish Church in Aberdeen for family and friends impacted by the crash.
4.15pm: British Transport Police (BTP) confirm three people died. It was later revealed the fatalities included the train driver and conductor, named locally as Brett McCullough and Donald Dinnie.
8.17pm: The Queen sends a message of condolence, following on from Prime Minister Boris Johnson and First Minister Nicola Sturgeon’s statements.
8am: The investigation into the fatal crash begins.
8.29am: The Scottish Fire and Rescue Service reveals four firefighters were injured while dealing with the incident.
9.20am: Colleagues pay tribute to train driver Mr McCullough.
12pm: Network Rail confirms it is to carry out detailed inspections of high-risk trackside slopes with similar characteristics to that of the crash site.
12.30pm: Network Rail boss Andrew Haines visits the scene, following on from Scottish Government transport secretary Michael Matheson’s visit. Mr Haines pledges immediate action over the derailment.
12.35pm: The Crown Office confirms a joint investigation by Police Scotland, BTP and the Office of Rail and Road is under way – in parallel to an independent probe by the Rail Accident Investigation Branch (RAIB).
1pm: Transport secretary Grant Shapps meets with emergency workers at the site of the derailment.
4.59pm: NHS Grampian confirms four patients have been discharged from Aberdeen Royal Infirmary. Two others remain in hospital, but in a stable condition.
6.20pm: Police Scotland confirm the name of the third victim as 62-year-old train passenger Chris Stuchbury.