Both men, one in his forties and one aged between 50 and 60, were shot in the head and died shortly afterwards, despite frantic efforts by several people to save them.
The victims, whose identities had not been disclosed by police last night, had walked across the road from the Prince of Wales pub in Cavendish Road, Balham, at about 2pm and were approaching a cafe called The Sandwich Shop when the gunman, who had been inside the cafe for some time, came out and fired two shots from a heavy-calibre pistol. The man jumped into a white Vauxhall Cavalier which was later discovered several miles away, burnt out.
Wendy Cramer, 34, was in her parked car near by when she heard the shots and screaming. 'I saw the two men lying on the ground. They were both still alive. I checked and found they had a pulse. I moved one of the men on to his back. They had both been shot in the head and were very still.
'At first I thought they were dead because their heads were such a mess. It was difficult to think that anyone could be alive with wounds like that.'
Daniel Hamilton, a car body repairer working in the garage, did not realise what had happened at first, but then rushed out and saw the two men lying in pools of blood.
Another woman, who wanted to be known only as Michelle, told how one woman passer-by who she thought was a nurse had given heart massage and mouth-to-mouth resuscitation to one of the men, though he died before the ambulance arrived.
Commander Tom Williamson, officer in charge of crime for the area, said police had few details about the men and were still trying to establish a motive. 'This was a cold-blooded, gangland- style execution. Quite frankly it's an assassination.'
He appealed for anyone who had seen the gunman, a white man in his twenties wearing a green three-quarter length Barbour jacket, blue jeans, white Reebok trainers and a red baseball cap, to come forward.
The D-registration Cavalier used for the getaway was found burnt out in Rosendale Road, Streatham.
Armed police arrested five people after cordoning off a street in Selsey, West Sussex, following the discovery of the bodies of two men - Jason Connors, 22, and Sean Farrelly, 24 - with gunshot wounds by a barman in the garden of the Star Gazer pub.
Police, who were still searching for the weapon used in the shootings, said the dead men had been involved in an 'altercation' following a karaoke evening on Thursday. One man was later released.Reuse content