Boxer Eamonn Magee Junior was stabbed to death in a crime of passion, police believe.
One main line of inquiry is believed to be that the 22-year-old - the son of former world boxing champion Eamonn Magee - was in a love triangle and killed in a jealous rage in the early hours of Saturday morning as a result.
A 32-year-old barber and part-time doorman was arrested on suspicion of murder a few hours after the brutal attack. Police said last night they had been granted another day by a court to further question the man arrested in connection with the murder of Mr Magee.
"There appears to have been a row between the victim and a man over a woman. This resulted in the murder of Eamonn Magee jnr. He didn't stand a chance," a source close to the murder investigation said.
Detectives believe that the young sportsman's killer lay in wait while he visited a friend in Summerhill Park in the Twinbrook area of west Belfast.
The engineering student's killer pounced as he went out of the house by the back door to check on a pizza delivery in the early hours of Saturday morning.
He was stabbed several times.
Detective Chief Inspector John McVea, who is leading the murder hunt, said: "Nobody would have known that Eamonn would have been coming out of the house to look for the pizza delivery, therefore we believe that the person was lying in wait for Eamonn as he would have come out of the house."
The knife used in the killing is believed to have been stolen from a property nearby which has been searched by police. Residents who were alerted to a disturbance tried in vain to save Mr Magee. He died shortly after arriving at hospital.
Friends of the tragic young boxer said he would not have wanted revenge for his death, which has left friends, family and the wider sporting community stunned.
His devastated mother Mary said she was struggling to understand why anyone would have wanted to harm her son.
"I have to bury my baby boy. What am I going to do? He was such a kind boy. He was such a warm-hearted boy, always was. I just can't work out why someone would do this to him... I don't know what I'm going to do," she told the Sunday Life.
His distraught father Eamonn snr added: "He was my blue-eyed boy, he was such a lovely guy, and I just can't believe it. I got a call at 3am. No father expects a call like that. I keep asking why it happened and can't come up with an answer.
"Eamonn was a really nice guy, everybody had a good word to say about him and he had a very bright future."
Eamonn jnr's boxing advisor and friend, Gianluca Di Caro, said he wouldn't have wanted revenge.
"He would want us to forgive, he'd be the first to want to give the perpetrator a second chance and as such I hope that I can be as strong as he was and have forgiveness in my heart - right now I can't see it but I will try," Mr Di Caro, who is vice president of the Malta Boxing Commission and managing director at WBU Europe, wrote on Facebook.
He added: "I really am devastated over this; we had great plans, Eamonn was destined to go all the way, he would have been a world champion... he was a smashing kid, he really was.
"I am devastated, truly heartbroken at such a senseless act of cowardice by some mindless fool. Eamonn was a gentle and caring person; that may sound strange to those outside the boxing world, but believe me Eamonn was a truly lovely kid, we loved him to bits and have to say we were and are so proud that he chose to trust us with his career."
The young man's heartbroken sister, Aine Maire Magee, said on Facebook: "My brother just lived life to the fullest. It wasn't his time to go. His life was robbed from him. RIP my handsome brother."