A father desperately tried to save his young son who had fallen into a stream beside the Royal Canal before the pair tragically died.
The father, named locally as Sean Sweeney, was on his way to visit relatives with his three-year-old son Lee when the tragedy occurred.
It is believed the toddler fell into the water before his dad desperately attempted to rescue him.
However Sean - who is aged in his mid 30s and is known as 'Curley' in the Ashington area - also got into difficulty.
The bodies of father and son were discovered by a passer-by, who immediately alerted emergency services.
Despite the best efforts of paramedics they were pronounced dead at the scene.
The shocking incident occurred at approximately 3pm yesterday in the Ashington Park area of Ashtown, Co Dublin.
Gardai sealed off the scene yesterday afternoon as senior detectives arrived to investigate the tragedy.
An ambulance arrived shortly before 6pm to remove the bodies of the deceased, as shocked locals looked on in disbelief. One local man described the incident as "truly horrific", adding that he knew the older victim.
"I would have known him to see. His family live near to where it happened, the two of them were on their way to the father's house," the local man said.
As the family of the victims gathered at Mr Sweeney's family home, a man believed to be related to the young child had to be restrained by gardai.
Despite the investigation being in the preliminary stages, gardai are not treating the deaths as suspicious and believe it was simply a tragic accident.
Local Labour councillor Brendan Carr said the community had been left "devastated" by the news. "Naturally, our heart goes out to the families involved in this incident. It is the second tragedy involving a child to occur in this body of water in recent years.
"It must now be a necessity to implement safety procedures and standards in this area," he said. The politician said the pair were in the area visiting a relative on Easter Sunday.
Cllr Carr said: "This man was originally from Finglas. He was a very nice young lad. He was bringing the child over to a relative to get some Easter eggs.
"He lived in Finglas and this was a short-cut home. "
North Dublin TD Noel Rock said: "This is an unspeakably tragic incident. Easter is always a time for family, so to hear of someone passing away tragically on their way home is truly sad. My heart goes out to the family, and to those affected by this awful loss."
A spokesman for Irish Rail confirmed that trains between Ashtown and Broombridge stations were stopped for 30 minutes after the discovery.
"At the start it was unclear if this was on rail or canal so we had to stop the train.
"It was stopped for around half an hour. There were a couple of hundred passengers on the trains at the time, but when they learned the circumstances they weren't too upset about the delay."