Mr Petrasiunas, 24, was stabbed to death with a machete outside a block of flats in Chervil Rise, Heath Town, just before 5.20pm on Monday.
So far no arrests have been made but police are hunting 20-year-old Sean Bulle over the attack.
Detectives say they have followed a number of lines of inquiry to track Bulle down, but have so far been unable to find him.
Mr Petrasiunas, originally from Lithuania, lived in Heath Town and had a one-year-old son called Kingsley-Clifford.
An air ambulance landed on a nearby car park and medics attempted to revive Mr Petrasiunas but he was pronounced dead at the scene. A post mortem is due to be carried out on Wednesday.
His devastated family paid tribute today, saying : "Rest in peace, I love you so much and always will.
"Your little sister will miss you too.
"We will love you forever my beautiful angel.”
Detective Inspector Jim Mahon, who is leading the murder probe, warned the public against approaching Bulle and said that anyone considering helping him risked being prosecuted.
He said: “We have been working hard to establish what happened on Monday afternoon and are following up a number of lines of enquiry.
“We believe Bulle may have been involved and I am asking for your help in tracing him.
“If anyone knows where he is or thinks they may have seen him, I would urge them to our incident room on 101, extension 861 3026 immediately.
“Anyone who may be shielding him through a sense of misguided loyalty, should be aware that they are committing an offence and could be prosecuted.
“It’s vitally important that we speak to Bulle. My message to him, is to do the right thing and let us know where you are."
Anyone who sees Bulle is asked not to approach him but contact police immediately.