Justice Minister Dermot Ahern has branded the killers as "scum" and pledged whatever is needed to get "these murderers off our streets".
While a Shannon Rugby Club spokesman, to which Mr Geoghegan was once attached, said he was devastated.
"Our shock has now turned to revulsion when you see that his life was taken for no reason whatsoever," he said.
Last night gardai were on high alert amid fears that the suspected killers -- members of the notorious McCarthy-Dundon gang -- will try to flee abroad.
Mr Geoghegan's remains were last night brought back to his mother's house -- just yards from where he was gunned down in the Kilteragh estate in the Dooradoyle area of the city.
Thousands are expected to turn up at the 28-year-old's funeral tomorrow, expected to be one of the largest the city has ever witnessed.
Mr Geoghegan's shocked team-mates at Limerick's historic Garryowen club described him as an honest and popular player who had friends across generations.
Gardai believe the rugby captain was targeted by criminals who intended to kill one of their drug dealing rivals in the quiet Dooradoyle area of the city.
He was shot dead after leaving a friend's house after watching the Ireland versus Canada match on television.
Eoghan Prendergast, Garryowen club secretary, said Mr Geoghegan's family had been left numb with shock.
"The family are just devastated and numb. It still hasn't sunk in yet, they just didn't expect it,'' said Mr Prendergast. "Shane was such a nice, decent guy who was well-respected by young and old alike.
"He represented the spirit of days gone by because off the pitch he really kept everyone together. Shane had great get up and go about him. We were so proud of him and he was just as proud of us."
Garryowen, one of Ireland's best-known rugby clubs, has sent messages of sympathy to Mr Geoghegan's parents, Tom and Mary, his brother Anthony, his girlfriend Jen and his uncle Tony, the club's junior vice-president. His funeral Mass will be held tomorrow morning at St Joseph's Church on O'Connell Street and a special memorial service is also planned at the club on Friday.
The murder took place in the Clonmore area of the Kilteragh housing estate at around 2am on Saturday morning.
Gardai appealed for information and said they believed the gunman travelled to the quiet estate in a dark coloured Renault Espace, later found burnt out in the Rossbrien area.
Mr Geoghegan, who had worked as a fitter, played for Shannon Rugby Club before moving to Garryowen 10 years ago.
"Our rivals at Shannon where Shane played as a youngster were the first to offer their condolences," Mr Prendergast said.
The prop captained the Garryowen third team against his old club side last Saturday just hours before he was killed.
Defence Minister and Limerick TD Willie O'Dea said he was horrified by the killing.
"It's an horrific case. A perfectly innocent young man, a well known rugby player, a well known local family, very respected family, obviously mistaken for someone else and shot down," Mr O'Dea said.