Two teenagers who killed an 88-year-old pensioner when her home was set on fire with a firework stuffed through the letterbox have been jailed.

Kai Cooper, 19, declared “people are going to get terrorised tonight” as he and a 17-year-old friend bought fireworks and two lighters in Romford, northeast London.

The teens set off fireworks in the street, aiming them at terrified pedestrians, a nearby restaurant and pub, and parked cars.

Cooper handed a Megaburst firework to the 17-year-old, who put it through the letterbox of Josephine Smith’s home.

The pensioner is believed to have been asleep in bed when the firework let off two successive explosions and set her home ablaze on October 28 2021.

The clock in her hallway stopped at 8.23pm when the fireworks went off, but it was not until nearly two hours later that neighbours smelled smoke and called firefighters, but Mrs Smith was already dead.

Sentencing the killers at the Old Bailey on Friday, Judge Mark Dennis KC said: “The victim was a vulnerable person who was in no position to protect or save herself from the fire that had been ignited downstairs in her home.”

Josephine Smith died in a blaze started when a firework was put through the letterbox of her home in Romford, east London

Cooper was found guilty of manslaughter and arson, while his friend admitted the charges. They both pleaded guilty to affray.

Cooper was sentenced to six and a half years in prison with an extra two years on licence, while the 17-year-old was sentenced to three years and eight months.

Prosecutor Heidi Stonecliffe KC said the younger teenager visited the Co-Op to buy fireworks but was denied by the shopkeeper due to his age.

However he simply handed money to Cooper to purchase the fireworks and got the older teen to also buy lighters.

At the time of the purchase, Cooper said: “I want something that is going to go far and quick” and his friend explicitly admitted the “aim was to fire them at people”, said Ms Stonecliffe.

Cooper said “I’m going to fire them at people’s faces”, while the 17-year-old told the shopkeeper he “wanted one that went ‘boom’.”

Cooper told his girlfriend: “Hey babes, come here. I’m trying to get fireworks, let them off at people. People are going to get terrorised tonight.”

CCTV captured the two teenagers firing the rockets in the street, “whooping” as passersby were left “trembling and terrified”, the court heard.

The pair were complete strangers to Mrs Smith as they approached her home in Queens Park Road, where she lived alone.

“They acted as a team as they did this, with Kai handing the 17-year-old the fireworks before they were lit and Kai encouraging (him) to do this”, said Ms Stonecliffe.

The 17-year-old took a Megaburst firework and ran across the road towards Mrs Smith’s house, where she was in bed and likely asleep. He then lit the firework and put it through the letterbox.

“It was a dare from his friend, with what can only be described as devastating, tragic, and ultimately fatal results”, said the prosecutor.

“A wall clock, perhaps rather poignantly, stopped at 8.23pm in Mrs Smith’s hallway when the firework exploded twice.

“It was 10pm that night that neighbours smelled smoke, when fire had been established for two hours.”

Mrs Smith was found dead in her upstairs bedroom, and efforts to revive her were unsuccessful.

Cooper denied at trial that he had encouraged or assisted the other teenager, but evidence from his own girlfriend confirmed he had been laughing as his younger friend ran across the road to Mrs Smith’s house.

Ms Stonecliffe said: “It was her view that (the 17-year-old) would not have put the firework through the door if Kai had not suggested it.”

The court heard less than 24 hours before the firebombing of Mrs Smith’s home, both teenagers had been involved in a brutal attack on a woman which was captured on film and posted on Snapchat.

Ms Stonecliffe said the first clip, shot by Cooper, showed the 17-year-old brandishing a large pole and “lashing out” to strike the woman.

In a second clip, the woman is on the ground as the teenager “used his feet to attack her.”

As Cooper repeatedly shouted “one boot to the face” and “stamp it”, his friend “stamped his foot on the woman’s face”, said the prosecutor.

Both teens admitted the attack and were sentenced to youth detention last year.

The judge received victim impact statements from Mrs Smith’s family but asked for them not to be read in open court because he believed it would upset the teenagers, who have mental health difficulties.

Jenni Dempster KC, representing the younger teenager, said he is “deeply and genuinely remorseful, and he never intended or sought the consequences that happened.

“He doesn’t seek forgiveness, but the regret and remorse he now feels is remarkable.”

Christine Agnew KC, for Cooper, said his conviction is “more than a wake-up call”.

“Mr Cooper appreciates - much too late in the day – the enormity and the stupidity of his actions in the days, months, and years leading up to that dreadful night”, she said.

A reporting restriction remains in place to protect the identity of the 17-year-old boy.