The carnage of the London Bridge attack could have been worse - one of the attackers had tried to rent a larger truck that could have killed more people, but his payment was declined.
The bloodthirsty gang was also shot dead before they could make their way back to the van where their petrol bombs were stored.
In a rare glimpse into the week long investigation, police released details on Saturday that showed Khuram Butt originally tried to rent a 7.5 tonne truck.
The intended truck was smaller but similar to the one used in the Nice attack last year that killed 86 people and injured hundreds in the resort town in the south of France.
After his payment was declined, Butt and his two accomplices rented a smaller van that they used to plough into crowds before they leapt from the vehicle and went on a stabbing rampage in an attack that left eight people dead and nearly 50 people injured. It was the third such deadly attack in Britain in three months.
After leaving the small white van, the men used 12-inch knives with bright pink blades, according to Dean Haydon, head of the Metropolitan Police's Counter-Terrorism Command.
Police also disclosed that multiple petrol bombs were discovered in the van, and a copy of the Koran opened at a page "describing martyrdom" was found at one of the attackers' houses.
Investigators believe three victims were killed on the bridge, including one man who was thrown into the Thames River, before the attackers left the vehicle and stabbed five people to death around London's busy Borough Market, Mr Haydon said. Police believe Butt was driving the van.
"When I come back to Butt trying to get hold of a 7.5 tonne lorry - the effect could have been even worse," he said.
More than a dozen wine bottles filled with flammable liquid and rags wrapped around them in the shape of Molotov cocktails were found in the van. Two blow torches were also found.
Mr Haydon said the men may have been planning even more bloodshed if they had survived their stabbing spree and made it back to the van.
Police also found a number of office chairs, gravel and a suitcase in the van.
Detectives believe the gravel may have been placed in the vehicle to make it heavier, or as part of a cover to justify hiring it, while the chairs may have been used to convince family and friends they were moving furniture.
The three attackers were wearing fake suicide belts consisting of plastic water bottles wrapped in grey duct tape.
Eighteen people have been arrested in connection with last week's attack. All but five have been released. Searches are continuing.
Butt, who police consider the attack ringleader, had been on bail after being arrested for fraud in a case in October of last year, police said.
He had also been repeatedly reported to police for violent behaviour and trying to recruit young children to Islamic State as well as featuring in the documentary, "The Jihadis Next Door," where he was seen next to a group of men unfurling a black-and-white flag scrawled with Arabic script and associated with the Islamic State group.