Reporter: Allison Langdon
Producer: Nick Greenaway
Thomas Kelly had his whole life ahead of him.
He was just 18 years old - with a promising job, a new girlfriend, some great mates and a close and loving family.
Then, one Saturday night, in a single, mindless act of violence, it was all taken away.
Thomas was walking along a busy street in Sydney's Kings Cross, hand in hand with his girlfriend, when he was viciously king-hit in an unprovoked attack.
Two days later, his mum and dad made the heartbreaking decision to switch off his life support.
We talk to the people closest to this tragedy - to Thomas' terrified girlfriend, to the mate who stuck by him during the mad dash to hospital. And to his parents, Ralph and Kathy, who are determined to give their son's death some meaning.
If you have any information about the incident, you can contact Crime Stoppers on 1800 333 000.
ALLISON LANGDON: Thomas Kelly had his whole life ahead of him. He was just 18 years old with a promising job, a new girlfriend, some great mates, and a close and loving family. Then last Saturday night, it was all taken away. Thomas was walking along a busy street in Sydney's Kings Cross, hand in hand with his girlfriend, when he was viciously king-hit in an unprovoked attack. Two days later, his mum and dad made the heartbreaking decision to switch off his life support. Tonight, as the hunt for the killer continues, we talk to the people closest to this tragedy - to Thomas' terrified girlfriend, to the mate who stuck by him during the mad dash to hospital, and to his parents, Ralph and Kathy, who are determined to give their son's death some meaning.
ALLISON LANGDON: The gentle serenity of the Southern Highlands of New South Wales is a long way from the bright lights and mayhem of Kings Cross. But a week ago, these two worlds collided with catastrophic results for the Kelly family.
RALPH: Having it happen to a son is beyond belief. We were a normal family up until Saturday night, and then something was taken away from us, and you don't think it will happen to you.
KATHY: There's a piece of us that's not there anymore. We're a family of five, we'll always be a family of five, but there's only four of us here. And I think, how do you ever come to terms with that?
ALLISON LANGDON: 18-year-old Thomas Kelly, Tom to his mates, was killed in Kings Cross - punched in the head by a complete stranger, leaving his parents Ralph and Kathy devastated.
KATHY: I sometimes have a bit of a talk to Thomas and just say I just can't believe you're not going to come home.
ALLISON LANGDON: It's also left the young women Tom was with that night, too scared to show their faces, with the attacker still on the loose.
GIRL 1: We could get hurt as well, because he's out there.
GIRL 2: Yeah.
GIRL 1: And I'm pretty sure that he knows that we were with Tom that night.
ALLISON LANGDON: So you fear retribution?
GIRL 2: Yeah.
ALLISON LANGDON: And it's mobilised an entire police force.
MARK: This coward who struck him didn't have an axe to grind with him. Thomas had done nothing to him. He was just intent, and this is why I say if it wasn't Thomas, it would have been someone else. This coward was intent on hurting someone.
ALLISON LANGDON: Tom Kelly grew up in a close, loving family, the elder brother, to sister Madeleine, and little brother Stuart. He was a cheeky but quiet kid, who graduated from the prestigious Kings School last year.
KATHY: He is here. Just there.
ALLISON LANGDON: He's so handsome.
KATHY: He is a handsome boy. I think he was just an average 18-year-old young man who wanted to be just like everybody else, he loved his music, he loved to get out on the rugby field, he loved tennis, he was quite a good tennis player.
RALPH: We've always brought our children up to respect other people and to be humble and to be honest and I think that Thomas really reflected all of those qualities in his life.
ALLISON LANGDON: You're clearly proud of him.
RALPH: More proud I think than you can reflect or you can talk about, because he was courageous. He would never give up.
ALLISON LANGDON: And life was really taking off for Tom, he had an accounting cadetship, and his first girlfriend. You were Tom's first love?
GIRL 1: Yeah. Yeah.
ALLISON LANGDON: What was it about him that was so special?
GIRL 1: I don't know. His personality, his morals. He was the most down-to-earth kind of person. Like, you couldn't just imagine him doing anything wrong.
ALLISON LANGDON: And like so many other teenagers, they were lured by the bright lights and raw excitement of Kings Cross.
GIRL 1: It was my first night at Kings Cross to go clubbing, so obviously I had a level of being scared. And I remember sending a message to Tom saying, "I'm a bit scared, you know, about Saturday night". But then Tom was like, "I promise that we're going to have a really good time together".
ALLISON LANGDON: So Tom was your protector on Saturday night? When was the last time you spoke to Thomas?
KATHY: I spoke to him on Saturday afternoon and we only spoke for a minute and, I just said, "Well have a nice time, or be careful," And he said, "OK mum, I'm going. Bye, I love you." And I said, "I love you too." And that was the last time I spoke to him, and I think you had a conversation with him too that day?
RALPH: Yeah, I spoke to him about six o'clock that night, and I said no, that's fine, just have a good night and be careful. And he said yeah, I will be careful, and same thing, I love you.
ALLISON LANGDON: This was meant to be a special night for Tom, his first time in Kings Cross with his first girlfriend, celebrating a mate's 18th birthday. The plan was to meet under the Coke sign, but not knowing the area, Tom and the two girls were dropped 150 metres off the main drag. How could they have known that such a short walk would be so deadly? The three 18-year-olds were walking up Victoria Street, just after 10 o'clock. A security camera capturing their last moments of innocence: Tom on the phone getting directions from his mate Andrew Mo. Seconds later he was attacked.
GIRL 2: I saw this guy. He was just standing with his back against the wall. And then he just walked up to Tom and punched him, like that.
ALLISON LANGDON: What do you remember about that actual moment?
GIRL 1: Him letting go of my hand and hitting the ground.
ALLISON LANGDON: Tom let go of your hand and fell backwards?
GIRL 1: Yeah. I just I didn't know what to do, kind of thing. We were all just stunned. It was just so shocking.
ALLISON LANGDON: Did you get a look at the man who did it?
GIRL 1: Not clearly, because it was dark.
MARK: This lunatic's just come across the two girls, the path…
ALLISON LANGDON: So basically right across the girls.
MARK: Yeah, right across the path of the two girls to deliberately attack Thomas;
ALLISON LANGDON: Assistant Commissioner Mark Murdoch is in charge of policing the Cross. Do we know whereabouts Thomas fell?
MARK: Literally where we're standing.
ALLISON LANGDON: Right here?
ALLISON LANGDON: And so this guy's punched him. What's he then done?
MARK: He's taken off.
ALLISON LANGDON: And he's headed up this way?
MARK: He's headed south in Victoria Street and run up towards the Coke sign.
ALLISON LANGDON: Within minutes Tom was being rushed to St Vincent's Hospital. His friend Andrew Mo, who organised the night out, was riding with him.
ANDREW: I can still see the image of Tom lying on a stretcher, blood all over his face, trickling down his hair and the paramedics doing all they can to just keep him breathing. He was wheezing for air. It's very vivid in my mind, yeah.
ANTHONY: This is the image of Thomas's skull. One of the most important factors is this area of white here is blood, and that's causing compression and reflects damage to the brain.
ALLISON LANGDON: Dr Anthony Grabs is head of trauma at St Vincent's. He says it wasn't the punch, but the fall to the ground, that did the damage. So he falls and hits his head here, and his brain is basically pushed in that direction.
ANTHONY: Yeah, it's decompressed that way and then goes back to the other direction.
ALLISON LANGDON: But the punch was enough to knock him out.
ANTHONY: A punch was enough to knock him out, which then resulted in the fall.
ALLISON LANGDON: So that's really the killer punch, isn't it?
ANTHONY: That is the killer punch, yeah.
RALPH: it was about 10:30, we were just getting ready to go to bed, and the hospital called about five minutes later and Kathy took the call and really couldn't comprehend what they were saying so she passed the phone to me, and they just said, "Look, we need you to come up to the hospital straight away," and I said, "Well, why?" and they said, "Because we just need you both here now."
ALLISON LANGDON: While Tom underwent emergency brain surgery, his parents made the frantic dash to be by his side. How did he look after surgery?
RALPH: I don't think I can give you the words that tell you how he looked, he was um…
KATHY: He really looked like he…
RALPH: He looked, he was…
KATHY: He'd already gone.
KATHY: From the moment we walked in there, his body was completely unmarked, but you know, I've never seen anybody like that in my life before.
RALPH: We still had hope. He was still was alive and…
KATHY: He was breathing, he was in a machine…
RALPH: …while he was alive, there was hope. And so that first night, we just sat by and held his hand and spoke to him.
ALLISON LANGDON: But within 48 hours, it was clear Tom had no chance of recovery, he was brain-dead. What did you get to say to him in those moments before you turned off his life support?
KATHY: How proud we were, and you know, I think I just kept calling him 'my darling boy'. You know, I don't think I've ever said that to his face, ever, while he was with us, you know. You just…
RALPH: I was begging him to come back, because he had been so strong in his life. I was asking him to be strong and to try, one last time, to come back to us. But he couldn't. Because we'd been told that his hearing was the last thing that goes. So you hope that he can hear, and we still had, right to the very end, we still hoped that that while he was alive there was still hope. And so I was asking him to come back and prove everyone wrong.
ALLISON LANGDON: I'm sure he heard those words.
GIRL 1: I still had Tom's phone case with me, and I remember just staring at it, just thinking "Oh, please come back."
ALLISON LANGDON: If there is one positive in this dreadful story, it's that Tom's death wasn't in vain. He may have lost his life in a senseless act, but by deciding to donate his organs, he saved the lives of others. It's another example of what a fine young man he was.
RALPH: We wanted something to come of it that would benefit other very sick people who needed his organs, and I know it's the right decision.
ALLISON LANGDON: Is there any solace in knowing that Thomas gave the gift of life to three or four people?
RALPH: Yes, absolutely.
KATHY: Oh, absolutely.
ALLISON LANGDON: But what the Kelly family is struggling with most, is why it had to be Tom. Why him?
KATHY: As much as you wouldn't want that to be anyone else's child, I just keep thinking just, if only he hadn't have been in that very spot at that very time and you know, if only the taxi had have stopped somewhere else, or if only you know he was 10 minutes late leaving home or any number of variables could've just changed this whole outcome and it's just, just impossible to believe that it's happened.
ALLISON LANGDON: And to try and prevent it happening to another family, the Kelly's have bravely gone on the front foot - doing whatever they can to help the police catch the killer, and stop the violence.
RALPH: The use of a hand is like the use of a gun, and that if you're going to punch someone it's like shooting someone. And that's the correlation that they need to understand, that it's a danger.
ALLISON LANGDON: That it's potentially a lethal weapon.
RALPH: It is a lethal weapon.
ALLISON LANGDON: Do you hate this person?
RALPH: Yes, and I hope that the justice comes to them soon.