Twenty-nine people including a woman with unborn twins died in the Omagh bomb on 15 August 1998 and over 200 people were injured.
The Real IRA bombing on the Co Tyrone town was the single worst terrorist atrocity in Northern Ireland.
At 12.40pm, a Vauxhall Cavalier containing the bomb left Dundalk.
The car had been stolen earlier in the week in Carrickmacross in Co Monaghan.
On the day of the bombing, the car travelled from Dundalk through Co Monaghan and Co Armagh before arriving in Omagh.
At 2.20pm, the car carrying the bomb arrived in Omagh and parked up in the middle of the town centre outside the SD Kells clothes shop.
The photograph shown above was found by investigators in a camera amongst the rubble.
It was taken shortly before the bomb exploded and shows the Vauxhall Cavalier where the bomb was lying, unknown to those in the town.
The first bomb warning using a recognised codeword was called into UTV at around 2.30pm which was then phoned into the RUC's emergency switchboard.
The warning mentioned that a 500lb bomb was on Omagh's main street near the courthouse.
A second warning was also phoned into UTV, along with a third one to the Samaritans' office in Coleraine.
After the warnings, police moved everyone from the top of the town near the courthouse down towards the supposed safety of Market Street.
However, the warning was inaccurate with many people moving right into the vicinity of the car bomb.
At 3.10pm, the bomb exploded in the middle of the crowd on what was a busy Saturday afternoon.
Twenty-one of the victims were thought to have been killed instantly in the blast which also destroyed a number of buildings.
A huge emergency response began with scores of injured people being ferried to the local Tyrone County Hospital.
A senior surgeon at the hospital later told an inquest that around 240 people arrived at the hospital within 45 minutes of the bombing, saying they faced "battlefield conditions".
The most seriously injured were later flown or driven to hospital including the Royal Victoria in Belfast and Alnagelvin in Londonderry.
It took until 10.45pm for the first initial death toll to be confirmed.
A police release said that 25 people had died so far, already worse than any previous terrorist attack in Northern Ireland.
It wasn't until September 5 that the final victim of the Omagh bomb died.
In all twenty-nine people died in the bombing, including a woman with unborn twins.
Want a quick and expert briefing on the biggest news stories? Listen to our latest podcasts to find out What You Need To Know.