When he was 25, then-soldier Jason McNulty, freshly arrived in East Timor, shook the hand of an Indonesian soldier. This small act became something he couldn't get out of his head for years afterwards, as he learnt of Indonesian atrocities against the East Timorese.
It contributed to the post-traumatic stress disorder that threw his life off the rails.
Private Danielle Close, a 21-year-old Australian Army intelligence analyst, was diagnosed with multiple sclerosis a little over a year ago. Not wanting her disease to define her, she threw herself into athletics and ultimately this year's Invictus Games in Toronto.
Squadron Leader Paul McGinty, an RAAF nurse who suffered tumours in his spine, has seen soldiers "come full circle" after evacuating them from the battlefields of Afghanistan with lost limbs, only to meet them years later competing in the games.
What they all have in common is that having served in the military and gone on to compete in the games founded by Prince Harry, they are part of what is widely described as a totally different sporting ethos.
Private Close has competed in plenty of sporting competitions before, but this is "the first event you go through where even the people you're against are backing you".
"Even if you come last, you still have everybody cheering for you. It's competitive but it's different. It's nothing like any athletics meet."
She won five medals in a dizzying range of events: gold in discus and indoor rowing, and bronze in the 100 metre sprint, shot put and rowing.
"Medals are nice but they don't mean anything at the end of the day," she said.
She's already given one medal away to a coach, saying that "four is enough for me".
Prince Harry, an Afghanistan veteran, initiated the Invictus Games. Toronto, the third games, was closed on Sunday by rock legends Bruce Springsteen and Bryan Adams. All up, the Australian team of 43 athletes won 51 medals. Next year it will be hosted by Sydney.
The Vice-Chief of the Defence Force, Ray Griggs, who was in Toronto, said the games "redefine what personal achievement is".
"It's not about the medals. It's about getting to the starting line. It's about watching a triple amputee in the pool being urged on by thousands of cheering spectators and emerging with a beaming smile and a real sense of accomplishment," he said.
Mr McNulty said he "lost a house, lost a business and nearly lost my family" because of the mental scarring he suffered in East Timor.
His downward spiral nearly ruined him but he pulled himself together in time to see his daughter grow up. A few years ago, he walked into a gym weighing about 130 kilograms and says he's "never looked back".
"Today, my bike is my psychiatrist," he said.
His daughter, now 10, was there in Toronto along with his new partner to see him win bronze in the cycling.