Detectives probing the arson murder of seven-year-old Joel Urhie have seized potentially crucial CCTV footage as they investigate whether the attack is linked to a gang dispute.
Joel was found dead after the blaze in Deptford, south-east London, on Tuesday.
His mother, Sophie, and 19-year-old sister escaped by jumping out of a first-floor window.
They were taken to hospital with non-life threatening injuries, where they were joined by Joel's brother, Sam, 21.
Sources said one line of inquiry was that the attack was gang-related amid reports Sam may have been the target.
But Detective Superintendent Jane Corrigan said the exact motive was still not known and there are no suspects in the case.
CCTV footage which may hold vital clues to Joel's murder was seized by detectives on Wednesday morning.
CID officers removed the box connected to the camera system from a flat on the other side of the road from Joel's family home.
Tien Thuan Nguyen, 56, said he had not watched the footage, but added: "I've got a camera. Police came and took (the footage)."
The camera at the rear of his flat does not point at the Urhie house but may have captured the person or people who started the blaze as they arrived at or left the scene.
Meanwhile a forensic team was combing the area for clues while uniformed officers conducted house-to-house enquiries.
Peter Hill, 69, who lives on the fourth floor in a neighbouring block of flats said he heard an "aggrieved bloke shouting his head off" in the early hours of the morning before the fire.
"I was lying in bed just next to the window, that's how I heard the noise," he said.
"I heard a male, a grown-up black male, shouting his head off.
"He seemed aggrieved, he seemed unhappy, he seemed pissed off. That's the impression I got."
Floral tributes have been left on the fence opposite the fire-ravaged house on Adolphus Street, where six fire engines and around 35 firefighters tackled the blaze after they were called at 3.25am on Tuesday.
Nearby properties were evacuated as a precaution and crews brought the fire under control just before 4.50am.
Family friend Grace Gbenedio, 56, said she visited Joel's family in hospital on Tuesday.
"They are doing well," she said.
She added she had spoken to Joel's brother Sam to ask how he was feeling and he said he is "fine as much as possible".
Asked about speculation that he could have been the target, she said: "It can't be possible."
She added: "I don't think anyone would be thinking he's a target. It's a shame people are thinking like that."
Alex Hope, 29, who knew Joel's brother Sam when they were growing up, said: "He was a nice kid. He used to play football here in the square."
Responding to reports Sam may have been the intended target, he said: "That would really surprise me if that's the case.
"I haven't seen him in a long time but growing up he was a lovely kid."
He added: "If that is the case it's a real shame because the mother is such a lovely person.
"It's just devastating. I would love to know what the actual reason is.
"No one deserves that and it's just a shame the little one passed away in such tragic circumstances."
A young father, who asked not to be named, was also surprised by suggestions that Sam could have been targeted.
"He's a good guy. He just looks like an average person who helps out his mum and I literally hear nothing bad," he said.
"I'm just really shocked, really sorry for their loss.
"The child didn't deserve that. No-one deserves that. It makes no sense, it's just tragic.
"I don't even think there could be reason on this Earth for that to happen. I don't care what happened in the past."
Friends and neighbours, including Elizabeth Okusanya, who visited Joel's family in hospital on Tuesday, was still struggling to come to terms with his loss.
"He was a quiet boy, easy-going and no trouble. He was very calm. It's really painful," she said.