It was a cold Saturday night in July 2012, when Ralph and Kathy Kelly received a phone call.

Thomas, their eldest son, had left home just after 6pm to attend a friend’s 18th birthday. He was more excited than usual, because it was that night he was planning on asking the girl he liked to be his girlfriend. He had never done that before, and had spent hours talking it through with friends.

They were meant to meet under the iconic Coke Sign in Kings Cross, but Thomas didn’t know the area particularly well, so got out of the taxi on Victoria Street about 200 metres away.

As Thomas and the girl he liked walked hand in hand towards the main street, an 18-year-old named Kieran Loveridge who had already been involved in altercations all over the city that night, spotted him.

LISTEN: Mia Freedman speaks to Kathy Kelly about the grief of her children on No Filter. Post continues below.

Kieran didn’t know Thomas. He didn’t know Thomas had a younger brother, Stuart, and a younger sister, Madeleine. He didn’t know how much Thomas loved playing the drums and the guitar, or how much he treasured his four pets.

He didn’t know that Thomas just wanted to kiss the girl he was holding hands with, or that he was full of dreams and ambitions.

Keiran didn’t know that when – for no reason at all – he punched Thomas in the face.

And that would be the last thing Thomas ever saw.

When the phone rang that night, it was St Vincent’s Hospital telling Ralph and Kathy that they needed to get to the hospital as quickly as possible.

Thomas Kelly. Image via Thomas Kelly Youth Foundation.

"I think I knew the moment I saw him that he was already gone," Kathy tells Mia Freedman on the latest episode ofNo Filter.

She doesn't recall how she reacted. There were lots of words and numbers and phone calls to grandparents and aunties.

The family were by Thomas' bedside two days later when they watched his 18-year-old heart, stop.

"The only comfort I have," Kathy says, "is that he didn't see anything coming... he was happy. He was contemplating how he was going to kiss this girl."

CCTV captured the perpetrator, and what followed was a torturous trial that played out in the public eye. Calmly, Kathy says, "the offender said the punch didn't kill Thomas, the pavement did."

The Kelly family watched countless character witnesses support Keiran, and at no point did they receive an apology from Keiran himself or the Loveridge family.

Keiran was first sentenced to five years and two months for his attack on Thomas. But in July 2014, the NSW Court of Criminal Appear re-sentenced him to a minimum of 10 years, two months jail, partly because of an increase in the minimum sentence for manslaughter from four years to seven.

Madeleine, Kathy, Thomas and Stuart Kelly. Image via Kathykelly.com.au

Stuart Kelly, then 16, said outside the courthouse, "I no longer have a brother, instead I have a hole in my life, and that's something I'm meant to accept... I can tell you firsthand that to experience this kind of pain at such a young age is just … it's just too hard."

But their sense of overwhelming injustice which began as anger, slowly turned into determination.

“How can you sit back and see your child has lost 70 to 80 years of his life and not fight for that? That’s where it starts”.

Ralph and Kathy began the Thomas Kelly Youth Foundation,with the Take Kare initiative, mirroring Thomas' initials. Take Kare is all about responsible drinking, and looking out for friends, family and strangers.

You can read about the Take Kare initiative, here, in memory of Thomas Kelly.

You can read about the Stay Kind initiative, here, in memory of Stuart Kelly.