Christopher O'Neill, in his late 50s from Ballymun, was shot once in the stomach by a man armed with a shotgun.
The gunman struck as O'Neill – known locally as 'The Walrus' – cycled along the street and was shot at close range. As the gunman fled, he fired another shot, wounding himself in the leg.
The gunman, who is in his 20s and from Finglas, attempted to escape down a laneway beside the bus stop towards Hillcrest Park, but managed to shoot himself after opening fire at his intended target.
He was found shortly afterwards by responding gardai.
Both O'Neill and the injured man have been brought to separate hospitals by paramedics where they are being treated for the gunshot injuries.
While investigations are at an early stage, it is believed the incident is linked to a criminal dispute.
It is understood that nobody else is being sought in connection with the double shooting.
A 45-year-old local man told the Herald he was bringing his daughter to a creche this morning at around 8.15am when he heard shooting.
"It was two shots. They sounded louder than bangers, so I knew they must be gunshots," he said.
Gardai were at the scene very quickly and arrived before ambulance crews.
"I could see when I got to where the shooting happened a man was lying in the front garden of a house and there were men standing around him blocking my view," said the man.
"There were bicycles lying on the ground and the man who was shot was regularly seen on his bicycle on the area, usually with one or two others on bikes," he said. "When the ambulance came he was carried out of the front garden on a stretcher.
"He wasn't making any sound," he said.
Paddy Gately (67) lives nearby. He said: "I'm a bit shocked, but it doesn't surprise me any more. This is a very quiet area around here, but these things are happening every day now."
"I do not think things are going to change because there is no punishment for criminals," Mr Gately said.
Gardai sealed off a large area on Glasnevin Avenue at a bus stop where the shooting occurred.
The laneway where the gunman attempted to escape was also sealed off.
O'Neill was rushed to the Mater Hospital, where he underwent emergency surgery for a gunshot wound to his stomach.
Three bicycles were lying on the ground behind the garda cordon and there were reports that another bicycle used by the gunman was found nearby.
Gardai at Ballymun appeal for witnesses to call them today at 01-6664400.
There were no arrests this morning.