On the edge of the Kenyan capital's second-largest slum, a woman clutching a baby in her arms is in tears.
By Karen Allen
BBC News, Nairobi
Police have moved into the corrugated tin-roofed Nairobi neighbourhood in search of weapons and members of the outlawed criminal gang, the Mungiki.
"They dragged me from my home and beat me...I don't know what's going on.
"We don't know who the Mungiki are, but the police are hitting everyone," she sobs.
In a week which has seen up to 30 deaths in this dirt poor neighbourhood, which has earned the nickname "Kosovo", the police are conducting a major swoop to weed out gang members.
The Mungiki, who claim to take their inspiration from Kenya's Mau Mau rebels, have been linked to a string of gruesome beheadings and attacks on police.
Following the tearful woman deeper into Mathare slum, an extraordinary scene unravels.
Vegetable stores, furniture shacks, small grocery stalls, or "dukkas", have been abandoned. The muddy footpaths are silent.
Everyone appears to have fled, apart from a woman and her children scuttling past the armed police who are busy kicking doors down.
A little deeper into the slum, across the river where young men at gunpoint are dredging the water for weapons and bodies, the full picture emerges.
Hundreds of residents, men women and young children, lie face down in the mud.
Policemen with assault rifles, pistols and AK47s watch over them.
A man with a head wound spits out blood and groans in pain. People ignore him.
Every now and again one of the captives is plucked out, dragged into a corner and questioned.
A woman in a brown dress screams in pain as she is questioned and kicked once again.
A policeman claims weapons were found under her bed at home. She says she knows nothing.
With claims of rampant police corruption in Kenya and allegations that weapons have been planted, it is impossible to know who to believe.
The operation was to show that the Mungiki will not be tolerated
It gets worse. A man with a blue and orange sports jacket is dragged passed us into a dark room.
Police follow him in - presumably to interrogate him.
Out of view shots are head. An hour later a body is carried out by a group of terrified boys.
A blue and orange top can be seen underneath a white tarpaulin shroud.
Similar scenes keep being repeated as the police operation continues. I count four bodies being brought out during the course of the morning.
An undercover detective confirms my worst fears. These are not the bodies of those killed in the shoot-out overnight. They are people who have been "executed" for failing to co-operate with police.
"What can we do," he says, hopelessly.
The papers claim that a dozen more people were killed in this operation.
Even by Kenyan standards this is ruthless, and the editorials in the morning newspapers are now calling for restraint.
Maybe the people who lost their lives were Mungiki, maybe they were not.
For some it makes little difference.
Those who live in Mathare are as afraid of the police as they are of the Mungiki gang.
One man told me: "We pay our taxes for the state to protect us, when they don't, we rely on Mungiki."
This is an area where people live hand to mouth. Most of the youth are unemployed and so crime and extortion are what pay. Violence is part and parcel of life here.
The evidence lies in a corner. A pile of weapons that police have recovered from homes include machetes, AK47s, and home-made coshes.
Intermingled are other personal effects: a lampshade, a box of tissues and a maroon-coloured Buddha that once sat on someone's shelf.
With elections just six months away, and fears that the Mungiki, who claim to have political links, could continue their violent campaign, ministers have appealed to the public for help.
Thursday's operation was designed to send the message that the outlawed sect will not be tolerated.
But what appear to be random beatings and a heavy-handed police operation will do little to inspire anyone to "rat" on the notorious gang.