Shannen Vickers and Pauline Adams were overcome by fumes
A teenage girl and her grandmother were murdered in a flat fire started over a £15 debt, a court has heard.
Shannon Vickers, 17, and Pauline Adams, 57, were asleep in the flat in Mile End, east London, in February when petrol was poured in and set alight.
David Philip, 19, and Jake Sheehan, 20, allegedly started the fire after arguing about money with a youth who also lived in the flat.
Mr Philip, from Bow, and Mr Sheehan, from Bethnal Green, deny murder.
The Old Bailey heard that Mr Philip and Mr Sheehan had a fight with an unnamed youth related to the women on 22 February.
Simon Denison QC, prosecuting, said Mr Philip owed £15 to the youth, who had been "letting it be known in the area that Philip didn't pay his debts".
Mr Philip and Mr Sheehan later complained that they had been sprayed with CS gas during the argument, the court heard.
At the end of the row, Mr Philip allegedly shouted at the youth: "We are going to burn your house down."
Mr Denison said: "It is almost beyond belief, but an hour or so later Philip and Sheehan carried out their threat."
The men allegedly siphoned petrol from a motorcycle, set fire to the vehicle then walked up to the fifth-floor flat.
They poured the petrol through the flat's letterbox and on to its door then set it alight, Mr Denison told the court.
"A major fire rapidly took hold. Thick black smoke and burning fumes filled the flat," he said.
"Pauline Adams and Shannon Vickers would have been asleep when the fire was set. They both woke up.
"Pauline went to Shannon's bedroom. Shannon was heard screaming for just a few seconds but she was not heard again."
Mr Denison said the pair were "overcome by the smoke and the fumes".
"They died together, lying side by side - two completely innocent people killed over a £15 debt."
Miss Vickers and Mrs Adams were the only people in the flat at the time of the fire.
The court heard that Mr Philip and Mr Sheehan made telephone calls to friends shortly afterwards confessing what they had done.
The trial continues.