Father-of-two Alistair Wilson, 30, was gunned down in Nairn in the Highlands on November 28 2004 as he prepared his children for bed.
His murder is still unsolved despite an extensive police investigation which remains live.
Police also revealed new evidence to the BBC about the blue envelope handed to Mr Wilson before he was shot.
Mr Wilson’s widow, Veronica, said she is grateful for the work the police have done but that the family need answers about who killed the husband and father.
She told the BBC: “For us as a family, we need to know why. This is just so senseless.
“For two young boys - aged two and four - to be left without a dad, that can’t be repaired.
“But a who and why would just make such a difference to us being able to move on.”
On the evening Mr Wilson was shot, his wife opened the door to a stocky man, aged 35-40, wearing a dark jacket and baseball cap and holding an envelope. He asked for her husband by name.
Mr Wilson spoke to the man and then went back inside to talk to his wife before returning to the door, where he was shot.
He died in hospital later that evening.
The gun was recovered from a drain near Mr Wilson’s home 10 days after his murder.
Police told the BBC that the blue envelope handed to him was empty and had the name Paul on it.
They also said that a gun identical to the murder weapon was found last year in Nairn.
Mrs Wilson said: “It’s harder the older the boys get. Obviously when they were little they were just told their dad had died, and he wasn’t there any more.
“They’re young men now so they just can’t understand it, why somebody would do it to their dad and why somebody’s not been caught. Justice is a huge factor and issue that they have.”
She added: “Everyone has supported us and the boys have had very few problems with being who they are, but it’s still very horrible for them to realise now who they are. It’s not nice being the banker’s widow or the banker’s children.”
Earlier this month police said the investigation is still live and urged anyone with information to contact them.
Detective Superintendent Gary Cunningham said: ‘’The investigation into the murder of Alistair Wilson remains open and ongoing and we urge anyone with new information or anyone who hasn’t spoken to police to speak to us so we can investigate all opportunities.”
Anyone with information is asked to contact Police Scotland on 101 or the dedicated inquiry number 0131 311 5916 or to contact Crimestoppers anonymously on 0800 555 111.