(CNN) -- He declared last summer to be a "dream come true," but now Oscar Pistorius has entered what could be one of the darkest periods of a life punctuated by extreme challenges.
Few details have emerged about what happened in Pistorius' upmarket Pretoria home around 4 a.m. that Thursday morning, leaving stunned fans at a loss to explain how their hero could have fallen so far and so fast.
Born with a congenital abnormality, Pistorius, 26, had both his legs amputated below the knee before his first birthday, but through sheer determination carved a career in world-class athletics.
In 2012, he became the first double amputee to compete against able-bodied runners at the London Olympics, adding to his fame as the "Blade Runner," a reference to his carbon fiber prosthetic legs.
While he failed to win a medal at the London Games, Pistorius' presence on the track was hailed as a triumph over adversity and the defeat of critics who claimed his blades gave him an unfair advantage.
For many, he was an example of what could be achieved through a potent mix of determination, positivity and skill.
Who was Oscar Pistorius, really?
Soon after his arrest, the athlete's image was being pulled from billboards, as admirers questioned whether an inspiring story had perhaps obscured a more complex character.
Was Pistorius violent? On the edge? In a story titled "The Fast Life of Oscar Pistorius" published in the New York Times, writer Michael Sokolove wrote: "Pistorius is, as well, blessed with an uncommon temperament -- a fierce, even frenzied need to take on the world at maximum speed and with minimum caution."
After the shooting, a police spokeswoman revealed there had been "previous incidents" at the home, including "allegations of a domestic nature" but did not say what they had been.
It was known Pistorius owned guns. He was a keen shooter and despite his disability he was not afraid to take risks. During a visit to Pistorius' house a few years ago, he showed CNN images of himself water-skiing, scuba diving and quad bike riding.
"I grew up in a family where disability was never an issue. We didn't really speak about my disability, not because it was a topic that was taboo... it was just never an issue. And that's the mentality that I've had," Pistorius told CNN's Piers Morgan in late 2012.
From a young age, Pistorius dedicated himself to being the best he could be at sport.
"I was never much of an academic at school so I had to find something which I enjoyed. I started sports and from a very young age, my mother said to us 'sports is not about being the best, but it's about giving your best.'
"You might make the second or third team, but losing isn't the one that gets involved and comes last, it's the person that doesn't get involved in the first place," he said.
Family, fans offer support
Support from Pistorius' family was firm and unwavering in the days after Steenkamp's death.
"We have no doubt there is no substance to the allegation and that the State's own case, including its own forensic evidence, strongly refutes any possibility of a premeditated murder or indeed any murder at all," said his uncle, Arnold Pistorius.
Even through their grief, Steenkamp's family failed to condemn the man accused of killing their daughter. Her father Barry Steenkamp told the Mail on Sunday: "There is no hatred in our hearts... he must be going through things that we don't know about."
Announcing the cancellation of five races this year in a statement in February, Pistorius' agent, Peet Van Zyl, referred to Pistorius as his "friend and a great professional athlete."
He said the athlete's sponsors remained "supportive" and that they "are happy to let the legal process takes its course before making any change in their position." Those sponsors include Nike, Oakley, BT, Ossur and fashion designer Thierry Mugler.
Thousands of people had sent messages of support from all over the world, Van Zyl added.
At the supermarket down the road from his house, parking attendant Andre Tsekedi told CNN that he saw Pistorius and Steenkamp a few days before the shooting: "They were holding hands and looked so happy."
Another, Samuel Motau, described Pistorius as "a very generous man. "He tipped us $10 every time. The only reason I never went to bed hungry was because of Oscar Pistorius."
As a child, Pistorius competed in water polo, cricket, tennis, triathlons and Olympic wrestling and boxing, before he smashed his knee while playing rugby at the age of 16. He took up track running as part of his rehabilitation, and within one year he was covering 100 meters faster than the existing Paralympic world record.
In 2004, Pistorius took his first gold at the Athens Paralympics and one year later competed against able-bodied Olympics for the first time, at the South African Championships.
Pistorius' career on the track suffered a setback in 2009 when he suffered serious head injuries in a boating accident. It took him almost eight weeks to recover, a period of time the athlete has described as "fairly difficult" as it marked the first season in four or five years in which he didn't record a personal best.
Soon after the London Olympics, Pistorius led his national team onto the track as South African Flag-bearer in the Opening Ceremony of the Paralympic Games. He went on to set a new world record in the 200-meter event but later suffered a shock defeat in the final, his first competitive loss over the distance in nine years.
During the very last track event of the Paralympics, Pistorius again picked himself up and smashed the 400-meter T44 Paralympic record in a time of 46.68 to take gold. It ended a summer he later described as "a dream come true," according to his website.
Beyond the track
Pistorius' determination to succeed has made him one of the world's most recognizable athletes.
According to his website, Pistorius is an ambassador for the Mineseeker Foundation, a non-profit organization that works to clear landmines worldwide.
When asked about his thoughts on being a role model, Pistorius told CNN: "I think it's a massive blessing.
"Obviously, being an international sportsman, there's a lot of responsibility that comes with that. So having to remember that there are kids out there, especially, that look up to you is definitely something that you need to keep at the back of your mind."
Pistorius has more than 260,000 followers on Twitter -- around 30,000 of those added in a few days since this arrest.
One post, on February 12, linked to an Instagram image of himself with a young boy on prosthetic limbs with the message, "In the run-up to the launch of my foundation in July I will give at least 10 kids mobility!"