"This is my son, my son," sobbed one old man in a video of the aftermath posted on YouTube, as he tugged in vain at the leg of a corpse lying face up, his blue shirt covered in blood.
The world is learning just how bloodthirsty the Shabiha can be. But inside Syria, their capacity for hideous brutality has long been known.
"Even before the revolution, any time there was unrest they would go out into the streets and stop it for the government," said Selma, who comes from a prominent Alawite family – a Shia Muslim sect, into which the Assad family was born, and to which almost all of the Shabiha belong. Her cousins are Shabiha.
"They would just break people's arms and legs. They would fight for Bashar to the death. It is natural – they have to defend their sect."
Her cousins wore civilian clothes, she explained – "then the television can say that these are just civilians who love Bashar."
Indeed, a survivor of the Houla massacre said he knew they were Shabiha, and not the army, because the men were wearing white trainers instead of black military boots. The white running shoes have grown into a terrifying sight for the people of Syria, who fear the ruthless, lawless Shabiha almost more than the army.
Tit-for-tat killings on both sides are on the rise, with the rebels and the pro-government forces both accused of carrying out attacks. But it is the Shabiha - whose name means ghosts in Arabic - who inspire the most terror.
President Assad, and his father Hafez before him, used the Shabiha to terrorise Syrians into obedience, brainwashing the militia into believing the Sunni majority was their enemy.
Alawites comprise about 12 per cent of Syria's population, and historically were persecuted by the Sunnis; living in poverty in the mountainous rural areas around Homs and the port city of Latakia.
Alawites, who split from the Shia branch of the Islamic faith in the ninth century, believe prayers are not necessary and do not fast or perform pilgrimages. Many of the key tenets of the faith are secret, adding to their mystique, although some scholars say Alawites have incorporated elements of Christianity into their creed. Sunnis see them as heretics.
After the fall of the Ottoman Empire, Syria's French rulers needed soldiers willing to defend the regime from a Sunni uprising, so they incorporated large numbers of Alawites into the army, who were only too happy to fight their Sunni "oppressors".
They became the most politically powerful sect in Syria, and the vast majority of the country's top intelligence and military officers adhere to the faith. It was from the army that Hafez al-Assad emerged to stage his coup.
Initially the Shabiha were a mafia clan, making money through racketeering. Selma, the Alawite with Shabiha family, said her cousins were "filthy rich" through smuggling in diesel, milk and electronics. "Anything to Lebanon that is cheaper in Syria, and whatever is needed in Syria from Lebanon," she said.
The ruling Assad family turned a blind eye to their criminal behaviour and violent methods. In return, the Shabiha became the Assads' fiercely loyal defenders and enforcers.
"They are fuelled by this belief that they are fighting for their survival," said Dr Azzawi. "Assad tells them that they must defend the government or else they will be destroyed; it's kill, or be killed."
Dr Azzawi, who now runs the Syrian Network for Human Rights from London, showed The Sunday Telegraph a video of the Shabiha in action.
An enormous man, identified on the video as Areen al-Assad – a member of the president's family clan – posed with his gun, grinned from the steering wheel of his car, and flexed his muscles. His huge bicep bulged with a tattoo of the president's face.
At the end of the video, the posturing Shabiha militants proclaim: "Bashar, do not be sad: you have men who drink blood."
"It is their motto," explained Dr Azzawi, who said that many of the men were recruited from bodybuilding clubs and encouraged to take steroids. "They are treated like animals, and manipulated by their bosses to carry out these murders. They are unstoppable."
Hamza al-Buweida, a Sunni activist from Qusayr province, told The Sunday Telegraph how he watched in horror as his childhood friend got sucked into the Shabiha.
"Even when we were at university he looked to Bashar like he was God. Nobody was allowed to say something bad about him.
"It is something in their religion that moves them. And state media is terrifying them that terrorists will kill them if Bashar falls from power," he said.
"The army gave my friend a gun, he started using it to shoot at the people in the demonstrations. The security forces gave him a special sense of identity."
The militia operated with blind devotion to the leaders, referred to as "muallim", meaning boss, or "khaal", uncle. And indeed, it was in many ways a family business.
Mr Assad's cousin Numir has taken over as one of the key rulers of the Shabiha – even though the government is careful to avoid direct association with the militia and their murderous acts.
How the men are paid is unclear, although many claim the Shabiha is funded by businessmen tied into the Alawite clique that dominates the government.
What is known is that the Shabiha have a strong economic motives for backing the regime. Foot soldiers can earn up to £120 for a day's thuggery – a fortune in Syria.
The regime has long supported the Alawites financially: in the 1980s President Hafez al-Assad built homes in the Mazzeh area of Damascus for poor Alawite labourers who moved to the capital. When the uprising began in March 2011, the residents thanked the regime by violently repressing any stirrings of revolt.
In addition to sectarian hatred and economic motives, the Shabiha have another reason for wanting to keep the Assad regime in power.
"Being linked in the minds of most Syrians to the government, the Alawites are absolutely terrified of retribution if the government falls," said Professor Joshua Landis, director of the Center for Middle East Studies at the University of Oklahoma.
"And that fear is probably pretty accurate. The Alawites will face very bad things if the Assads are forced out."
Indeed, reassuring the country's 2.1 million Alawites that they will not be targeted in a post-Assad Syria is one of the key aims of the opposition, alongside encouraging ordinary Alawites to defect.
Of the Syrian Network for Human Rights's 239 dissidents inside the country, only 19 are Alawites. Of the Syrian National Council's 311 members, only five to ten are Alawites.
One of the most prominent Alawites on the council is Monzer Makhous.
"The Alawites are supporting Assad because they have been told that he is protecting them, and are very afraid about what will happen when he goes," he told The Sunday Telegraph. "But I don't think there will be revenge against them. Syrian people want peace.
"It is a big challenge for the SNC to attract more Alawites. The Shabiha are killing them too, if they try to leave. But we need them on our side."
Other Alawites agree that more should be done to encourage defections.
Oubab Khalil, an Alawite in Texas from the Syrian Expatriates Organization, said that many were willing to desert the president.
"Assad appointed himself guardian of the sect, but it's certainly not true that all Alawites support him," he said. "Assad has targetted Alawites too.
"They are there in the demonstrations, but are more afraid of turning against him."
But are economic reasons, sectarian hatred and fear of the future really enough to drive someone to slit a child's throat? Selma thinks so.
"If they know the whole area is against the regime they have no problem killing everybody," she said. "That is how it works."