It is believed that the young girl was struck by a vehicle in the tragic accident.
She was rushed to University Hospital Sligo where she later passed away.
“Absolutely devastating such heartbreaking news. My thoughts and prayers with her family, god give them strength somehow, rest in peace little angel,” one person said.
“Heartbroken for this little girl and her family and for the community of Enniscrone,” added another.
A third shared: “Everyone's worst nightmare. R.I.P. little girl. Something so tragic can happen in a split second. The poor family and driver, their lives will never be the same again.”
“So unbelievably heartbreaking condolences to her family. Rest in peace little one,” another said.
Another added: “Such devastating news to hear this eve, absolutely heartbreaking for her family, may the little angel rest in peace. God look over her family, you all are in my thoughts and prayers.”
One person offered their blessings with all who worked to try and save the young girl.
"Hard to know what to say when something like this happens,” they wrote. “I hope her family are surrounded by loving and caring people. God bless all involved today, the driver, anyone who saw it happen, ambulance crew and nurses involved in trying to save her life.”
Local Sligo County councillor Michael Clarke said: “It’s a holiday town and there are thousands of people here every weekend, it’s a terrible shock.”
“At a time when a lot of people are enjoying themselves, it’s very upsetting for a lot of people.”
“Condolences to the family, are thoughts are with them.”
He also told Ocean FM: “It’s an awful tragic situation for the family involved. A loved, beautiful four-year-old girl, lost. How they are going to cope with it, is nobody’s understanding.
"The whole community is in deep shock and sadness for the family and our condolences go direct to them and all the people involved.”
The incident occurred at a caravan park overlooking Killala Bay.
A spokesperson for An Garda Siochana said: “Gardai and emergency services attended the scene of an incident in Enniscrone, Co Sligo.”
“A four-year-old child was injured during the incident.”
“She was taken to University Hospital Sligo where she has since passed away.
“A family liaison officer has been appointed to support the family at this time.”