ONE morning 5½ years ago, Bill and Cheryl McCormack sat in a room at Victoria Police headquarters and tearfully pleaded for an end to the epidemic of senseless violence on Melbourne's streets.
Their son Shannon - a popular and gentle 22-year-old with a mop of curls - had been felled by one punch outside a city nightclub, hit his head on the footpath and died after spending a week in a coma.
''You read in the media every week on the Monday that someone's kid has been bashed inside a nightclub or in the city somewhere, and you just think to yourself, 'Thank God it wasn't my son.' On Monday it was our son. It wasn't somebody else's son, it was our baby, our gentle Shannon,'' Mr McCormack told journalists.
But the McCormacks' plea was to no avail. The years since have seen a roll-call of young men killed in their prime or horrendously injured in unprovoked attacks - Matthew McEvoy (2008), David Mitchell (2008), Justin Galligan (2008), Cain Aguiar (2009), Luke Adams (2009) - culminating this week with David Cassai.
The flood of tributes to the 22-year-old on Facebook - used all too often as a memorial in these times - paints a picture of a music-loving extrovert, a joker with a smile etched on his face.
We don't know what his attacker looks like. The man who ended Mr Cassai's life and left a family sunk deep in grief is on the run, hunted by the homicide squad and doubtless hoping no member of the pack he ran with that night develops a conscience. Police arrested two men on Tuesday night - and they are helping police.
Victoria Police Deputy Commissioner Tim Cartwright told Fairfax Media on Tuesday that despite high-profile cases such as Shannon McCormack's, there was still a steady trickle of similar attacks every year.
While emphasising that he was talking in a general sense, rather than about Mr Cassai's death, Mr Cartwright likened ''alcohol-fuelled, unprovoked, cowardly'' one-punch killings to domestic violence and road deaths, in that people once considered them to be inevitable.
''If we take that view - that it's always going to happen - we're certainly not going to fix it,'' he said.
Mr Cartwright said television and movies created the false impression that when someone was knocked out, they always regained consciousness, got up and walked away. ''That's simply not true, and people need to know that. These punches kill or cause serious brain damage,'' he said.
Nothing will ever begin to match the anguish of a parent who loses their child, and it is made worse by the perceived leniency of sentences.
Jacob Polutele, the thug who punched Canadian man Cain Aguiar outside a Yarraville pub in 2009, was sentenced to a minimum of seven years in prison for manslaughter. At the time of the attack, Polutele was on a suspended sentence for knocking another man unconscious.
Fostar Akoteu, who stomped on Mr Aguiar's head, also received a minimum of seven years for manslaughter, and a third man, Sioeli Seau, spent 12 months in prison for assault.
Andriyas Tello pleaded guilty to manslaughter after punching Matthew McEvoy twice in the head outside a city nightclub in 2008 and was sentenced to eight years' jail with a five-year minimum term. Lauren Sako pleaded guilty to manslaughter for kicking Mr McEvoy's head as he lay on the ground and was sentenced to six years' jail with a three-year minimum term.
''We ask young people to think about the consequences of their actions,'' Mr McEvoy's family said at the time. ''We still find it difficult to understand the senseless attack on Matthew.''
Laws introduced into State Parliament last month create two new offences of intentionally and recklessly causing serious injury with gross violence. People guilty of these offences will be jailed for a minimum non-parole period of at least four years, except in special circumstances such as mental illness.
The man who killed Shannon McCormack has never been identified, despite a $100,000 reward for information leading to his arrest.
''Every day we grieve in silence and relive our son's last week in intensive care and the horror when the doctors pronounced our son dead … It was our worst moment and one we never forget,'' Cheryl McCormack said last year on the fourth anniversary of the fatal punch.
''No parent should have to endure the death of a child, especially when it was such a senseless, cowardly act.''