Joseph Richardson, 61, stabbed his wife of 35 years with fishing knives and beat her with an ornament before trying to kill himself.
His friend of nearly 25 years, Michael Heath, said he was "absolutely shocked" at the news that his long-time fishing companion had murdered 57-year-old Janette Richardson at their Musselburgh home.
Mr Heath, owner of Mike's Tackle Shop in Portobello's High Street, said Richardson had dropped in to buy new equipment just two days before and discussed his fishing plans for the weekend.
Mr Heath said he had since heard rumours that joiner Richardson had spoken of killing his wife to fishing buddies a week before the killing. But the 50-year-old said he believed his friend "snapped in the heat of the moment" and gave no sign that he was set on premeditated murder.
He described Richardson as "an absolutely lovely man who lived for his fishing and always had a smile on his face".
He added: "Joe had only been in two days before to buy new wire boom. He was telling me about a few trips he had planned, including one for that weekend. He seemed his usual cheery self.
He would occasionally say things like, 'I'll have to clear that with the wife' when he talked about the trips, but we all do that.
"One of my customers told me Joe had been talking a week before that he planned to kill his wife. But we heard so many rumours afterwards so I'm not sure how much to believe it.
"I think he probably snapped in the heat of the moment. But I never saw any signs of this happening as he was always cheery.
"I might even have sold him the fishing knives he used to kill his wife, I don't know."
At the High Court in Edinburgh yesterday, Richardson pleaded guilty to murdering his wife, a nurse, at the family home in Musselburgh's Stoneybank Drive.
The court heard that mother-of-four Mrs Richardson was unhappy in her marriage and ready to leave her husband. She had been in contact with an old friend, Graham Walker, who lived in England, and kept in touch by calls, texts, social networking site Facebook and occasional meetings.
Advocate depute Joanna Cherry, QC, said: "The accused found this state of affairs extremely distressing and blamed this man for the marriage break-up."
She added that Richardson had "reacted adversely" to a suggestion by his wife that if they were to divorce she would be entitled to a share of the marital home and his pension.
Richardson phoned Mr Walker on 27 November and told him "You are going to feel like I feel" before hanging up.
A worried Mr Walker called the couple's eldest daughter, Joanne Greenhill, who went to her parents' home and found the couple lying on a bloody bed.
The judge, Lord Doherty, who will have to fix a minimum term under a life sentence for the murder, continued the case for sentencing to August.