Alistair Wilson was gunned down on his doorstep

Detectives said a man came forward following a call to the BBC's Crimewatch programme and has since been excluded from their investigation.

Mr Wilson, 30, was shot dead on his doorstep in Nairn on 28 November.

Detective Chief Inspector Peter MacPhee has appealed to another potential witness to contact police again.

A private memorial service for Mr Wilson will be held on Monday.

Mr MacPhee, who is leading the inquiry, urged someone who contacted the confidential helpline Crimestoppers, but hung up during their conversation, to call again.

Envelope clue

He said the Crimewatch appeal had yielded a number of interesting calls.

They included one relating to an envelope given to Mr Wilson at the time of the shooting, but which later disappeared.

A potential witness said they had seen a man with an envelope.

Mr MacPhee said: "We received information from Crimestoppers this week about a phonecall made to them with information relating to the murder inquiry.

"We are very interested in what this person had to say and we would like to speak to them.

"I feel the person has something more to tell us.

"In relation to the weapon found in Seabank Road, forensic examination continues and I am expecting preliminary results back next week."

The suspect for the shooting is aged 35 to 40 and was wearing a baseball cap and a dark blouson jacket.

Officers are still trying to establish a motive for the killing.

A man spotted on a bus has been ruled out of the inquiry

After the attack, the gunman walked down Crescent Road towards the links area of the town where he is believed to have escaped.

Veronica Wilson, Mr Wilson's wife, was joined by his mother and sister during the Crimewatch appeal.

Since the shooting, Mrs Wilson and the couple's two young sons have been living under armed guard at a secret location.

Mrs Wilson said the man who murdered her husband must be caught before she and her family can get on with their lives.

Crimestoppers has offered a �10,000 reward for anyone with information leading to the arrest, charge and subsequent conclusion of the case.

The helpline can be contacted on 0800 555111.