Their hair flopping over their eyes or tied back, these young men were doing something too old for their years, honouring a lost mate, doing it with such dignity, remembering the stories that made them laugh about 17-year-old Adriaan.

"He had the biggest heart and the best smile.'' "Adriaan was such a beautiful person through and through.'' "Adriaan was always the one to cheer people up.'' "We were all very lucky to have Adriaan in our lives.'' "It was physically impossible not to like him.''

"I love you Adriaan.''

These were the words that rung out from these loving teenage boys in front of hundreds of mourners on Friday at the Presbyterian Church of St Andrew in Forrest.

As minister Russell Smidt told them: "Thank you young men. You did a hard thing, but a good thing''.

Adriaan, who lived in Yass and attended Campbell High School, was killed after an incident with a log during a physical education class at Mount Ainslie last Thursday.

His life was just beginning. One of his friends said he felt happy to go for a drive with Adriaan after he got his P plates, acknowledging also that so many teenage milestones had been snatched away.

"When he was in that car, he looked so free and ready for the next chapter in his life to begin,'' his mate said.

"It's sad you won't get your braces off, or get to drive a fancier car, but I'll make sure I do those things so you're with me. Always.''

Adriaan's parents Christiaan and Sandra and sister Christelle had been comforted by the outpouring of love shown to them by friends, family and strangers since the tragedy.

Mrs Roodt was going to ask a friend to speak on her behalf but then decided to bravely stand and address the congregation herself. She said it had become clear "we are not alone in our grief and heartache'' and that Adriaan had touched the lives of so many people.

"We take comfort knowing Adriaan knew that we loved him,'' his mother said.

"And he knew that we were proud of him. We told him this often, if not daily.

"I actually phoned him on the morning of the accident just before school started to check that he had arrived safely at school.

"My last words were to him were: 'Love you lots'. Something that we actually say often, and keep saying, to our kids."

Mrs Roodt said the family were also buoyed knowing Adriaan had been raised in a loving, well-adjusted environment, always having fun at school and at his part-time job at KFC.

Even in his final moments, they knew he was being his happy self.

"We take comfort believing that he had fun with his mates on Mount Ainslie, right until the very end," she said.

His mother said she was also happy her son had experienced falling in love, making special mention of his girlfriend Jenna Smith.

"Jenna, you made Adriaan so happy and we will forever thankful to you for loving him," Mrs Roodt said.

In turn, a message from Jenna to Adriaan was read on her behalf by Frances Brown, director of missions, Calvary Public Hospital.

"You had big dreams of becoming an electrician like your father and your ambition in life was to make your parents proud," Jenna's message read.

"You had the ambition to do anything you put your mind to and that's what made you, you."

Jenna said she knew Adriaan would have grown into "a man who would be strong".

"I know I can't change time, but if I could do this all over again, I would tell you, you meant everything to me and you were my world," her message read.

Leading the service, Minister Russell Smidt, from the Gungahlin-Ngunnawal Presbyterian Church, said the loss of Adriaan made them realise "how much young people mean to us".

"He made people smile. We realise how hard Adriaan worked, maybe not at school. But he would push himself to exhaustion in the boxing ring. Earn every dollar he needed at KFC to pay for his KFC addiction,'' Mr Smidt said, to laughs.

"He showed kindness. He would offer his last piece of KFC to a mate. Or his mum.''

Mr Smidt said little more than a week ago, no one in the church could have contemplated being there.

"It's a time to cry out, 'Why?'," he said. But also a time for people to love and support each other.

The Roodt family moved from South Africa to Australia when Adriaan was eight. His funeral service in Canberra was filmed so that it could be played at a service for the teenager in Johannesburg on Saturday.

Mrs Roodt said so many people had supported them in their grief.

"Please know, we appreciate every message, every card, the flowers and the meals delivered to our house,'' she said.

"Thank you.''

The service ended with Amazing Grace and Adriaan's father Christiaan and his friends from school and work carrying his casket from the church on a beautiful, warm spring day.