They arrived bristling with heavy weapons and waving black flags from about a dozen Humvees, seized from the Iraqi army and supplied originally by the United States.
When the terrified residents looked out of their windows, they saw that Kosho, their traditional walled village in the mountains of northern Iraq, had been surrounded by jihadists. More than 200 bearded militants had besieged the village.
Then their leader -- a local man from Mosul rather than the foreigners who make up more than a third of the ranks of the group now known as Islamic State -- offered them a chance to save their lives.
'He told us that either we become Muslims or they would kill us all,' said Falah, mayor of the village made up mainly of members of the ancient Yazidi sect. 'We offered money but they would not accept it.'
The deadline the people of Kosho have to meet is midday today. Since the residents refuse to betray their faith, it is feared an entire village of about 2,500 innocent people might be slaughtered in cold blood.
'If we did not have families, we would try to escape,' the stoical Falah told me yesterday. 'But we have lots of women here and many children, along with all the old men and women of the village. How could we leave them?'
This is thought to be the first time these blood-drenched fanatics -- who delight in boasting of their barbarism and posting sickening murder videos on social media -- have threatened to wipe out an entire village.
Even by their own chilling standards, re-drawing the Middle East map with a rampage of rape, beheadings and revolting crucifixions, this marks a new low.
It comes at the end of a week during which the fanatics of Islamic State --formerly the Islamic State in Iraq and the Levant (ISIS) -- shocked the world again by advancing further into Iraq, prompting the US to renew military operations there for the first time since 2011.
Furthermore, having captured first the strategic city of Sinjar, then a string of other towns and the country's largest hydroelectric dam, they are just 25 miles from Irbil.
This thriving city filled with Western oil firms is the capital of Iraqi Kurdistan, the solitary success story following the disastrous US-led invasion of 2003.
As US jets started bombing again to protect Irbil, I found its churches, construction sites and parks packed with thousands of Christians and Yazidis fleeing the feared Islamists. Thousands more are trapped in searing heat on parched mountains to the west. The latest advance began a week ago when shots were heard in Sinjar late at night. Four hours later, the feared Kurdish peshmerga forces retreated, much to everyone's surprise -- followed by 150,000 residents fleeing for their lives.
Sinjar is an historic centre of the Yazidis, one of the world's oldest religions. Followers are seen as devil-worshippers by Islamic State because of their unique beliefs.
About five Yazidi and 40 Shia Muslim families were last night stuck in the city after failing to get out in time, hiding in fear from the bloodthirsty militants in their own homes.
I spoke to one Yazidi woman, living largely in one back room with her 60-year-old mother, two sisters and one brother eking out dwindling supplies of bread, rice and water while keeping lights turned off to avoid attention.
Her hushed voice quivering, she told me of hearing frequent gunshots and seeing Islamic State vehicles patrolling the streets outside. 'We are just sitting and trying not to move too much,' she said. 'We feel so scared. We do not know what to do. We cannot fight them and if we leave the house we will be killed or kidnapped. Afterwards, her despairing cousin, an engineer in his mid-twenties, told me in flawless English that their family felt helpless but could not mount an escape bid.
A respected local leader told me how Islamic State turned up at two Yazidi villages last week, telling residents they would be left alone if they surrendered all their weapons.
At the first village of Qana, the militia then killed 32 men before taking away the women. At Hezan, the second one, all the women were reportedly stripped naked before about 70 men were shot dead.
One terrified woman in her sixties jumped off the third-storey roof of her home, preferring suicide to seizure. Another, a newly-married woman aged 26, is said to have stabbed herself to death. It is impossible to verify such stories. But alarmingly, there are growing claims from a multitude of sources that Islamic State is kidnapping 'infidel' women for sexual slavery.
An official for Amnesty International who has spent the past few days with refugees confirmed that both men and women were being kidnapped by the militants: 'People fear the women are being raped and sold into slavery but we just do not know the truth yet.'
The rapid advance of the jihadists combined with the sudden fragility of the previously-feared Kurdish peshmerga has led to massive movements of frightened people.
One army officer told of a battle last week in which his two Kurdish battalions lost 100 men compared with just 30 jihadists killed.
'Everything they have is American -- it is all the latest equipment with the big guns, the Humvees,' said the Kurdish soldier, highlighting the failure of America's $2 trillion attempt at state-building since its botched intervention with the British.
One activist said 61,000 Yazidis turned up overnight in a northern Iraqi town behind the mountains, then disappeared northwards the following day. A refugee camp holding several thousand people from Mosul since its fall in June emptied in one panic-stricken hour on Friday.
Many of the worst scenes are on the mountain range near Sinjar. A doctor there with 5,000 other Yazidis told Human Rights Watch that ten to 15 people were dying daily, mainly from dehydration. 'No water, no food, no rescue, no way out,' he said.
Resala Shangali, a 26-year-old journalist, spent four days without food and just one slug of water desperately avoiding the advancing Islamic State forces with hundreds of other Yazidis.
She saw one infant die of dehydration and have to be dumped on the ground by his fleeing mother, another two-year-old fall over and die of a head injury, then five old people die one night alone.
On the second day, a woman gave birth, then both she and the baby died within half an hour despite several women trying to save them.
'That night was the worst because my clothes were covered with blood from trying to help her and I could not sleep,' she said.
Thousands of Christian, Yazidi and Kurdish refugees have lost everything and suddenly find themselves living in rubble-strewn building sites and crammed churches and feeling bewildered and betrayed.
Again and again yesterday I heard tales of families fleeing for their lives, many forced to pay huge sums for their survival to a group estimated to be the world's wealthiest jihadist gang thanks to kidnapping, extortion, bank raids and oil sales.
Often they were given a choice to pay money, convert to Islam or die. Among them was Elias Ibrahim, a Christian taxi driver from Mosul who earned $500 a month. He was told he could stay if he handed over $450 a month to the insurgents.
Twafiq Aboosh, 64, a wealthy hotel owner and farmer, was returning home when he was ambushed.
The Islamists forced him and his four children to lie on the ground with guns to their heads while quizzing them about their religion, then ordered them to leave their property without looking back at it.
'I have lost everything,' he said.
Nearby, in a half-built car showroom I found a primary school head teacher, his father and several staff living with their large families among the dust and debris.
Although Muslims, they were targeted since they were Kurds -- just as their people were previously victims of Saddam Hussein's appalling atrocities and gas attacks.
They have seen their lives spiral into sudden degredation and despair. 'These Islamic State people are not Muslims but murderers,' said Hussein Zeewer, the 37-year-old head.
'They shame our religion. It is even worse than Saddam.'
