The body of Lee Slattery, 24, from Ballynanty was found in a shallow grave at Knocklisheen near Moyross.
He had been shot three times, once in the head.
Members of the McCarthy Dundon gang are suspected of carrying out the murder over a drugs debt.
One of the main suspects is aged 17 and known for his extreme violence.
Addressing mourners at the funeral Mass in St Munchin’s Church, Canon Donal McNamara described Mr Slattery’s murder as “barbaric”.
“I would say this morning, in the name of God and of the people of Limerick I urge you please to end the violence in our streets.
“Yes, we must denounce the culture of violence and hatred that leads to the taking of another life. God is the giver of human life. And He alone must be the taker of human life.
“When we take it upon ourselves to take and destroy the life of another person, we are stepping into an area in which we have no right and no business.”
Canon McNamara said he had been 37 years ordained and had served in the Limerick diocese all that time.
“This is the first funeral of this kind – where a young man’s life has been taken brutally – that I have carried out. I sincerely hope and pray to God it will be the last.
“Watching Lee’s family who are so highly thought of in the neighbourhood, a family now so distraught, heartbroken and torn apart would leave anyone’s heart break,” he said.
Lee Slattery, he said, was a good man who adored his young daughter Aleesha, with whom he spent a lot of time, and he was always there for her.
Canon McNamara said another family has been left asking the question “why us? and why in this barbaric way?”
He added: “There is the extra and anguished question, why did it have to happen in this way?”
Following the Mass, city mayor Kevin Kiely met with the bereaved family outside the church and sympathised with the dead man’s parents, Ray and Rose, his brother Ray and sister Lorraine.
The funeral cortege passed near the spot where Mr Slattery’s body was discovered by gardaí, as it moved to Ballycannon cemetery.
Gardaí, meanwhile, are understood to have made important discoveries of potential evidence during the huge murder investigation.