Police investigating the fatal stabbing of a teenager in front of his parents at their Cardiff home say one theory is that it was mistaken identity.
Aamir Siddiqi, 17, was murdered by two masked men who broke into the house in the city's Roath suburb on Sunday.
On Tuesday evening, officers cordoned off a shop in a nearby suburb as part of the murder investigation.
South Wales Police said neither the shop nor its occupants were "in any way" directly involved in his death.
Police said they had gone to a shop in Cathays following "one of many positive lines of enquiry as a result of an excellent response from the public to our appeal for information".
Detectives said the mistaken identity theory was "clearly a hypothesis" at this stage. Aamir's parents were also stabbed as they tried to protect him.
Officers are hunting two Asian men in their 20s.
Meanwhile, police and relatives have appealed to the city's Asian community for help in finding the killers.
The A-level student was described as "a gentleman" and as "kind, sensitive and really funny" by his family.
His sister, Nishat Siddiqi, told a press conference on Tuesday that her brother was an upstanding young man, much loved by his family and friends.
She said the family were "devastated by the departure of our beloved Aamir".
She added: "He was a dearly loved and loving brother, son and friend to many. Even within our own family Aamir was a friend, something precious that we will miss."
Nishat Siddiqi made a plea for information about her brother's murder
Ms Siddiqi said her brother was a "genuine" and "sincere" person.
"We are worried in our own grief that the people who have committed this crime may do this again," she added, appealing for help in tracing them "before they hurt some other family".
Aamir's uncle, Dr Ahmed, spoke in Urdu to appeal to members of the Asian community for help.
A team of 60 officers are involved in the investigation and an incident room has been set up at Cardiff Central police station.
Officers said the Siddiqi family were "understandably going through an unbelievably traumatic time".
Two masked men killed Aamir Siddiqi at his family home in Cardiff
Police said two men armed with a "bladed weapon" forced their way into the end terrace house in Ninian Road in the city suburb of Roath at around 1340 BST on Sunday.
Det Chief Supt Stuart McKenzie, who is leading the investigation, said: "It is clearly a hypothesis of ours that Aamir was mistakenly targeted.
"But that forms part of a number of hypotheses we have got. We have got to keep an open mind in this investigation."
He added: "Aamir was an upstanding member of the community... and I can't understand why he was targeted in this fashion so mistaken identity is something we are considering."
Aamir's parents, aged 55 and 68, suffered stab wounds as they tried to protect their son.
Stephen Wilson, Cardiff Academy described Aamir Siddiqi as a lovely boy and a true gentleman
One suspect is described as being in his late 20s, of average height, with a stocky build. He had dark hair and was wearing dark clothing.
The other was in his early 20s, of slim build, and 5ft 11in (1.8m) tall. He was wearing a white jacket with a grey stripe down the sleeves.
As they were leaving the area they were seen pulling black knitted balaclavas over their faces, said police.
Anyone with information is asked to contact the incident room at Cardiff Central Police Station on 02920 571530 or Crimestoppers anonymously on 0800 555 111.