Janet, 65, can vividly remember the evening her 11-year-old granddaughter arrived at her house last year and said she had seen someone being given CPR on the playing field yards from her front door.

They were shocked to learn that a 19-year-old man, Shawn Seesahai, . They were even more horrified when they learned that the two perpetrators were just 12 years old.

“It’s just unreal to think they can do it. You think kids their age should be playing. You don’t expect a 12-year-old to cause the injuries like he had,” she said.

Janet, who asked not to give her surname, said one of the convicted boys was a known troublemaker who had been terrorising the neighbourhood for months, often roaming the streets in the early hours of the morning.

“He would be throwing bricks at windows, or snowballs at windows when it was winter. It’s a lot quieter now,” she said. “We didn’t feel safe going out when we knew he was about – we used to walk the dog on the field but we stopped doing all that because of him. I would never go out after dark.”

The behaviour was out of character for this area of , local people said. The streets of mainly semi-detached houses are quiet, with well-maintained gardens and neighbours chatting in the street.

At about 3pm, children from the local primary school filter out of the playground and across the playing field where Seesahai lost his life last November. Dog walkers meander past the bench he is said to have run from chased by boys brandishing a 42.5cm-long machete.

There have been some problems with teenagers congregating on this grassy area, though. “Especially at the weekend, we get a lot of people hanging around that field. There’s always a group of people here or on the bench. Sometimes very young, sometimes older. There’s always broken bottles left behind,” said Parmbir Singh, 28.

Alarm is growing about the number of young people carrying knives on the streets. Knife-related crimes increased by 8% in the West Midlands from 2022 to 2023, and numbers have been growing nationally since the pandemic.

Malachi Nunes runs Ambitious Lives, a mentoring programme for young people at risk of violence across the West Midlands. He said he had worked with children as young as nine in Wolverhampton who were carrying weapons, and said a “12-year-old today is thinking like an 18-year-old”.

“I was mentoring a young boy from Wolverhampton who was nine, and he was in fear of being caught up with the rival gangs because he had a brother in a gang,” he said. “A lot of young people have a kill-or-be-killed mentality. I think it’s a case of survival mode.”

He said the ready availability of such weapons had turned them into “fashion statements”. “People are on Snapchat posting that they’re selling Rambo knives for £40, or there’s WhatsApp groups as well,” he said. “It’s like: ‘Do you have one?’ ‘I have one.’ ‘Do you have the guts to carry it?’ A lot of it is all done on social media.”

For the staff at the Way Youth Zone in Wolverhampton, the city’s main youth service provision that caters for 85 to 150 youths every evening, it is why getting children away from screens at home and into a safe space after school is so important.

“We try to proactively discourage people from using social media while they’re here, and especially with the juniors we try to keep them off Instagram and TikTok,” said the charity’s chief executive, Paul Snape.

“The need for youth centres is absolutely essential and that isn’t just about tackling knife crime, it’s about giving young people the opportunities that they deserve and should have.”

Nikita Kanda, 24, whose 16-year-old brother Ronan, was yards from his front door in 2022, said Seesahai’s murder was “opening people’s eyes” about how these incidents could happen anywhere.

The family live less than three miles from where Seesahai was murdered, on an equally ordinary residential street where the violence that took Ronan’s life came out of the blue.

He was killed by Prabjeet Veadhesa, then 16, with a 55cm-long ninja sword he had ordered online using his mother’s ID to pass security checks. He had collected a cache of 30 weapons, selling them on to friends at school.

Ronan’s family believe an obsession with large weapons as status symbols is fuelling knife crime murders, and they are the sale of all bladed weapons online.

“People might say, well, they can use a kitchen knife, but it’s more about the culture surrounding these weapons. [Veadhesa] wasn’t obsessed with Russell Hobbs kitchen knives, was he? He was obsessed with big knives,” Nikita said.

In Seesahai’s case, the weapon was a black machete, bought by one of the boys from a friend of a friend, who he would not name. One of the boys posed for a photo with it hours before the killing, wearing a mask.

“You can see kids aged 12, 13, 14 get really influenced by each other, for example with vaping. The same kind of thing will happen with machetes and knives,” Nikita said. “That 12-year-old might have brought [the machete] into school. He could have gone and showed his mates, ‘look what I’ve got’. And they’ll say ‘oh I want to get one now, it’s so cool’.

“How many other kids are doing this now? How many other kids have these weapons enclosed in their rooms?”