A supermarket is the focus of a police investigation of claims a nine-year-old boy was locked in a storeroom and “bashed against walls” for stealing a bottle of Coca-Cola — igniting a debate about vigilante attacks on out-of-control children.

The West Australian can reveal police were yesterday speaking to staff at the supermarket in Perth’s south-east after the boy’s outraged family claimed he was “dragged around” before being padlocked in a “cage” at the back of the store.

Relatives of the boy claimed he was assaulted, thrown in the storeroom and padlocked inside. It is believed he was causing trouble in the store with other children who ran to the boy’s home to alert his family.

The boy escaped from the storeroom by smashing a window, cutting his arm as he made his escape.

The incident, which happened last weekend, comes amid a spate of complaints about out-of-control children across Perth.

Ellenbrook residents have spoken of their frustration at living in a “war zone” after a six-year-old boy was filmed leaping between the roofs of homes.

And Maddington residents said they were under siege from a gang of violent children.

Staff at the supermarket refused to speak to The West about the incident yesterday. Police confirmed they were investigating.

The boy cannot be charged because 10 is the youngest that children can be held criminally responsible in WA.

“Poor baby will be traumatised for the rest of his life,” one relative wrote on Facebook in a post that also said he was taken to hospital by family for treatment on his cut arm.

Gerry Georgatos, the national director of the National Indigenous Critical Response Service, said he had been made aware of the incident and was ready to assist the boy’s family.

Mr Georgatos said it was a “grim reality” that there were many “lost youth” across Perth.

“But despite the frustrations of proprietors, it is important not to overreact and it is important to take matters into context,” he said.

“They had an obligation of duty of care to their staff and an opportunity to contact police.

“As a community, our focus should be on how do we help our lost youth, not how do we exacerbate problems and demonise them.”

Criminal lawyer Simon Watters said vigilante action was rightly condemned by the courts but that the law did recognise the right of citizens to make arrests.

“If they had detained him in there while they had called the police and were waiting for police to attend, then that would be something you would think would be OK,” he said.