Witnesses told the High Court in Glasgow how they tried to stop the bleeding as Javaid Ali lay at the back of his store in Green Road, Paisley, on June 15, last year.
They were giving evidence at the trial of Lee Anderson, who denies murdering 48-year-old Mr Ali by stabbing him on the neck and wrist with a knife at the Sunshine Licensed Grocers.
Eileen Meechan sobbed as she told prosecutor John Scullion that blood was coming out of Mr Ali's neck like a fountain.
Grandmother Miss Meechan, 48, told the jury Mr Ali was at the back of the store on his phone and staring at her. Seconds later he collapsed.
Miss Meechan said: "I noticed the blood was coming out of his neck like a fountain. I ran out the shop and then ran back in and phoned an ambulance."
Alan Nimmo, 34, from Paisley, told how he got a nappy and put it in the wound in Mr Ali's neck to try to stem the blood.
Anderson denies murdering Mr Ali. The trial continues.