The heartbroken parents of a young health fitness entrepreneur found stabbed in the street have urged his killers to "do the decent thing" and hand themselves in.
The mother of James Brindley asked "how they can sleep at night" at an emotional press conference on Tuesday, in which his parents made a public appeal for information.
New CCTV footage of two suspects has also been released, just over two weeks since the 26-year-old's death, late on June 23.
James had been on a night out with friends in town and was walking home when he was attacked, suffering a single stab wound to the heart.
He was on his mobile phone chatting to his girlfriend at the moment he was assaulted in Little Aston Road, Aldridge, West Midlands, police also confirmed.
Immediately afterwards, four schoolboys rushed to his side and tried in vain to save his life with first aid.
His father, Mark Brindley, said the family were "living day to day", after the incident in James' home town.
Holding hands with James' mother Beverley, the couple described the terrible blow dealt to the family, including their younger daughter and James' little sister Charlotte.
They urged people to view the new CCTV footage and help detectives in the investigation.
Mr Brindley said: "If you know anything that can help the police in their inquiry no matter how trivial it might appear, please come forward because as family we need to know who did this."
He turned to his wife, as she told reporters: "We need to know why."
Asked how he felt about his son's attackers, Mr Brindley said: "I couldn't repeat it - they really ought to do the decent thing and hand themselves in."
Mrs Brindley said: "How they can sleep at night, how they can continue on a day-to-day basis, is beyond me.
"So if there is anybody that has seen any change in anybody they are associated with, they live with, has this person suddenly gone on holiday?
"Please come forward, no matter how small - it will make a difference and we need that."
James had been a budding entrepreneur and was about to open a health fitness business in the Walsall area, his parents said.
Describing their son as "bonny" and "loyal", they added he tended not to go for nights out because he had been saving money to plough into his business.
Meanwhile, the family praised the "overwhelming" support of strangers, friends and family, with Mrs Brindley adding "that is what's giving us the strength and the courage to carry on".
Police believe the two men pictured in the fresh CCTV footage, recorded as they walked in the Whetstone Lane and Churn Hill Road area, hold the key to cracking the case.
Detective Chief Inspector Chris Mallett, leading the investigation, said: "We're releasing some footage of two people we believe to be responsible for the attack on James."
He added: "This is a significant development in our investigation and I would urge anyone who recognises either of these men to contact us as a matter of urgency.
"James' family desperately need answers but we also need your help to bring James' killers to justice."
A £10,000 reward is being offered for information leading to a conviction.
Mr Mallett added: "Only one of these two individuals will be responsible for inflicting that fatal wound.
"And we therefore urge the other person who was involved to come forward and contact us."
Anyone with information is urged to ring police on 101 or call Crimestoppers anonymously on 0800 555111.