Many wore black Friday to demonstrate against the high levels of violence against women in the country.
Others focused their attention on Pistorius and his fascination with fast cars, cage fighting and firearms.
Those who knew Pistorius, including a former girlfriend, weighed in on social media.
Trish Taylor, mother of Pistorius' ex-girlfriend, Samantha Taylor, wrote on Facebook: "I'm so glad Sammy is safe and out of the clutches of that man."
But another ex-girlfriend, Jenna Edkins, took to Twitter to defend him.
"All I am saying is let him speak, let his side be heard without jumping to conclusions," she tweeted, offering "love and support" to the Pistorius family.
"I have dated Oscar on and off for 5 YEARS, NOT ONCE has he EVER lifted a finger to me or made me fear for my life."
At the defense request, the chief magistrate delayed a bail hearing until Tuesday for Pistorius, who was ordered held in a police holding cell, rather than transferred to a prison.
In seeking a premeditated murder charge against Pistorius, prosecutors appear to be claiming they have evidence the athlete planned the killing ahead of time, said William Booth, a prominent Cape Town defense lawyer.
Such a serious charge makes it more difficult for Pistorius to successfully apply for bail, Booth said, though it could also be a challenge to get a conviction.
"It's quite difficult to prove that in a situation where there isn't a witness," the defense lawyer said. "If I just plan it in my mind and I arrive at somebody's house and there's no witnesses and I shoot the person, it's really tough for the prosecution to show that planning."
Pistorius made history at the London Olympics last year when he became the first double-amputee track athlete to compete at any games. He didn't win a medal but did make the semifinals of the 400 meters and the final of the 4X400 relay, propelling the world's best-known Paralympian to the level of an international track star and one of the world's best-known sportsmen.
AP Sports Writer Gerald Imray reported from Johannesburg. Associated Press writer Michelle Faul in Johannesburg contributed to this report.
Jon Gambrell can be reached at www.twitter.com/jongambrellAP . Gerald Imray can be reached at www.twitter.com/geraldimrayAP .