KEY witnesses are being sought by detectives in a renewed appeal to trace a robber who threatened a terrified granddad at gunpoint and said he would blow his head off.

A month after the shocking incident police have renewed their appeals for information and are urging anyone who was in the area at the time to come forward.

The incident happened on Easter Monday, April, 9, at 5.30pm when retired psychiatric nurse Baah Heyford was walking through Queen's Park.

The 67-year-old was approached by a man who held a gun to his head and asked him to empty his pockets. The offender was then pulled away by one of his friends.

Officers are unsure whether the weapon was real or an imitation, but say they are treating the incident very seriously.

Det Sgt Jonathan Holmes said: "This was an extremely serious incident where a retired man was walking through his local park and was threatened with a handgun.

"He believed he was going to be shot which was extremely distressing and he was left very shaken.

"We believe there will have been other people in the park who may have witnessed the incident. You may think the information you have is not significant but it could be crucial to our investigation."

Speaking after the incident Mr Heyford said: "I thought right this is it, my time is up. I thought I was a dead man."

The offender was Asian, of stocky build, aged 18 to 24 and about 6ft 2ins, with dark hair, and a clear complexion..

A 20-year-old Blackburn man was arrested but later released without charge.

Witnesses should contact police on 0845 1 25 35 45 or Crimestoppers anonymously on 0800 555 111.