At the head of a procession that chanted "enough is enough" was Anene Booysen's distraught foster mother, Corlia Olivier, who recounted the moment last weekend that she saw her daughter dumped amid the gravel and grass, her stomach slit open down to her genitals.
"I heard her saying 'Mommy help me, Mommy help me' and I rushed over ... and just saw her guts hanging out," Olivier told reporters, tears welling up in her eyes.
Booysen was found by security guards lying only a short distance from her house after partying at a nearby bar on Friday evening in the sleepy town of Bredasdorp, 130 km (80 miles) east of Cape Town. She later died in hospital.
Like the gang rape and murder of a 23-year-old student on a New Delhi bus last year, the incident has stirred rare outrage in a country where many people have become desensitised by some of the world's highest rates of sex crimes.
President Jacob Zuma expressed "shock and outrage", calling for the harshest possible sentences for the killers and a concerted campaign "to end this scourge in our society".
South Africa has the highest number of reported rapes per head of population of any Interpol member country.
Even when suspects are caught, only 12 percent of cases end in conviction, and sexual crimes - even in the most serious cases - seldom spark much beyond some soul-searching editorials and anguished radio phone-ins.
The Womens' League of the ruling African National Congress (ANC) is trying to mobilise the public into something akin to the mass protests against anti-female violence that broke out in India after the New Delhi attack.
On Friday, Cape Town radio station KFM started broadcasting a "bleep" every four minutes as a reminder to listeners that another South African woman will, on average, have just been raped.
At the Bredasdrop building site, religious leaders and politicians linked arms with Booysen's
relatives as they sang hymns and laid a wreath by the cross, adorned with a single pink ribbon.
"I still hear her footsteps," Olivier said, turning to accept a vase of flowers from an elderly couple, as a stream of well-wishers arrived to offer condolences.
Maree Louw, the commander of the local police station, said the murder was one of the worst cases she had seen in a long career. The first police officers on the scene have been receiving trauma counselling.
"The brutality and the slaughter of this young teenager is beyond belief," Louw told Reuters.
Like many towns in South Africa's Western Cape, Bredasdorp, with a population of 35,000 people, has its problems with drug and alcohol abuse but Louw said most people would go to bed at night with their back doors open and windows unlocked.
Booysen managed to reveal the name of one of the attackers, a family friend, before dying.
Three men in their early 20s have been arrested and are expected to appear in court on Tuesday on charges of rape and murder.
They face the prospect of life in prison if convicted.
Under a constitution drawn up after the end of apartheid in 1994, Nelson Mandela's "Rainbow Nation" abolished the death penalty. Some in Bredasdorp wish that were not the case.
"This crime was very sadistic and deserves the death penalty," said mother-of-three Sophia Europa. "What they did was worse than anything done to an animal."