A well-known criminal was shot several times in the head at around 8pm in the Lucan area of Dublin.
Gardaí are investigating the discovery of the man's body at Griffeen Valley Park in Lucan.
The man was well known to gardaí as an extremely violent, dangerous and unstable individual.
A car was found burned out nearby, it is understood a firearm has also been recovered.
Originally from Ballyfermot, the man had previous convictions for violent crime and firearms offences.
He was also questioned about the rape of a 15-year-old boy and he was a suspect for a number of murders, including those of Darren Carey and Patrick Murray whose bodies were found in the Grand Canal at Karneystown in Co Kildare 14 years ago.
Two crime scenes have been sealed off for forensic examination tomorrow.
Tánaiste and local TD Frances Fitzgerald has condemned the attack.
She said it "is another reminder of the callous disregard for human life displayed by people intent on murder and mayhem".
"An Garda Síochána will continue to take every possible measure to counteract activity of this kind and will have the continued support of the Government and the community in doing so.
"Every effort will be made to bring the perpetrators of this dreadful shooting to justice and we will face down those who mistakenly think they can get away with these evil acts," added Ms Fitzgerald.
Gardaí have begun a murder investigation and have appealed for anyone with information to contact them at Lucan Garda Station on 01-6667300, the Garda Confidential Telephone line on 1800 666 111 or any garda station.
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