One theory is Aamir Siddiqi was the victim of mistaken identity
Tributes have been paid to a 17-year-old boy who was stabbed to death in front of his parents by masked men who forced their way into his Cardiff home.
A-level student Aamir Siddiqi's parents were also stabbed as they tried to protect him from the attack at Sunday lunchtime in the city's Roath area.
Sher Ali, a neighbour and family friend, said Aamir was "very, very good - he was lovely".
Aamir's headteacher described him as "very bright" and a "major loss".
Mr Ali, who is president of the Cardiff branch of the UK Islamic Mission, had known Aamir since he was a young boy.
"As a boy, he was very, very good - he was lovely," he said.
"He was getting on in his education, Islamic education, very well, because he used to be a student in the mosque.
"He never had trouble with anybody and he respected all the people. He would come to me and ask 'how are you' and shake hands."
Mr Ali added he had had "a very bad shock" when he heard the news, and all the people who knew Aamir were praying for him.
"It must have been very bad people who have done this without any reason.
"I know his parents and they are very good people, educated people and they never had trouble with anybody," he said.
He said the Muslim community he was part of had offered the family any help they needed.
"[Aamir's father said] thank you very much, if I need anything I'll let you know," Mr Ali added. "But unfortunately in this kind of matter, nobody can help, you see."
Stephen Wilson, principal of Cardiff Academy where Aamir was an A-level student, said in all the years he had been teaching he had never known anything as tragic as Aamir's murder.
He told the BBC many of the staff at the small and closely-knit school, which he likened to a family, had been on the phone to him in tears, to say nothing of the students.
"He's a major loss - a lovely, lovely boy. Very outgoing, very bright, he had a place to read law at Cardiff University and was certainly on course for grade As," he said.
"A very eloquent boy. You only have to read the Facebook pages, the tributes to him, which say more than I ever possibly could.
"In every way, this is such a brutal attack. No-one really understands what has gone on, why it happened.
"Aamir really was the kind of boy who was a gentle man. He never had a bad word to say about anyone."
Mr Wilson mentioned the importance to Aamir of his Muslim faith, adding: "He kept his beliefs to himself but he lived by those beliefs, and everybody really loved him."