GARDAI investigating the circumstances surrounding the death of 23-year-old Dean Fitzpatrick in Dublin last night have arrested his stepfather.
Dean was the brother of Amy Fitzpatrick, the Dublin teenager who went missing in Spain in 2008.
Amy was 15 at the time of her disappearance.
His body was discovered at Northern Cross on Malahide Road, Dublin 5 at around 11.20pm last night.
It is believed that he received a number of stab wounds.
He was taken to Beaumont Hospital but pronounced dead a short time later.
David Mahon(43) has been arrested by detectives investigating the murder.
Speaking about the fatal stabbing Superintendent Ronan Galligan said: "We're satisfied it is a murder.
"The individual suffered a serious injury and he died as a result of those injuries and we have launched a murder investigation here at Coolock Garda Station.
"A male in his early 40s has been arrested and is presently being detained in connection with the incident.
"It's obvious that some altercation took place and unfortunately Dean died as a result of the injuries so anybody who has any knowledge of what went on should contact us here at Coolock Garda Station."
The scene has been sealed off pending a full technical examination by the Garda Technical Bureau.
The office of the State Pathologists office has been notified
Gardaí are appealing for anyone who may witnesses this incident or who may have information to contact them at Coolock Garda Station 01-666 4200, the Garda Confidential Line 1800-666-111 or any Garda Station.
Investigations are continuing.