More than 1,000 messages of support and tributes have been left on an online book of condolences for Mark O'Sullivan ahead of his funeral in Kanturk today.
Mr O'Sullivan, 26, was shot dead in a bedroom of his home in a tragic murder-suicide that claimed the lives of three family members at farmlands in North Cork on Monday.
The bodies of his brother Diarmuid and father Tadg were found in a field nearby.
It is believed a dispute over inheritance sparked the violence.
Diarmuid and Tadg were buried together yesterday.
Friends, relatives and mothers from across Ireland have left messages of support for Mark's mother, Anne, and paid tribute to him ahead of today's funeral.
Mark was described as a "cheeky, kind-hearted, gentleman" who left a lasting impression on his friends.
More than 1,200 people left messages on his online book of condolences.
Many of the messages were from women, describing themselves simply as "a mother", wishing God would grant Anne O'Sullivan the strength to "carry such a heavy cross" and deal with her "unimaginable grief and pain".
One friend of the deceased wrote: "Mark, your kindness, gentle nature and beautiful smile will leave a lasting impression on me forever.
"I pray you get the peace you so deserve.
"I pray especially for your mom, that God gives her the strength during this time and for all your family and friends."
Another message said: "I had the pleasure of working with Mark over the last 10 months.
"A wonderful young man, whose work ethic, diligence, commitment and positivity was a tremendous example to all of us who worked with him.
"Mark will be sorely missed by all of us.
"My heart aches for you, Anne, you are in my thoughts and prayers. May Mark's gentle soul Rest in Peace."
The former UCC student said: "Mark was a true gentleman.
"He made my time at UCC more enjoyable than I thought possible.
"He will be missed by his peers and friends alike."
Another wrote: "Mark was in my year in Coláiste Treasa.
"He would open the door and let you go in before him."
A fellow law graduate wrote: "Mark didn’t just make my time in UL better, he made my life better.
"Mark will always be my best friend.
"Funny, kind, caring and selfless.
"You were a joy to know and you’ll always be in my heart, thoughts and memories.
Mark’s funeral will take place privately for family members only at the Church of the Immaculate Conception, Kanturk.
It will be live-streamed at 3.30pm this afternoon.