Groups of youths wielding pangas and axes were taken in three buses to the Nairobi estate where they ran amok, killing 20 people and injuring at least 30.
The buses - one green and another brown - dropped off the raiders a short distance from where the attack began, on Kamunde Road in Kariobangi North, a witness said.
He spoke up as the government set up a special team to investigate the cause of the fighting - and Opposition leaders demanded the immediate resignations of security minister Julius Sunkuli and Commissioner of Police Philemon Abong'o for failing to stop the violence.
Both the police and the provincial administration were warned of the attacks by Kasarani MP Adolf Muchiri.
He said he had alerted the police on three different occasions, and that each time they assured him they had people on the ground ready to handle any outbreak.
A vigilante group leader said he too had warned the police three times of the impending attack but they had failed to act.
Residents attributed the violence to the long simmering dispute over rent and threats by some landlords to send in Mungiki members to enforce their demands.
However, Mungiki sect leader Ndura Waruinge denied his members' involvement in the Sunday night massacre.
An uneasy calm returned to Kariobangi, as police patrolled the streets and businesses began to reopen.
Shaken householders said they feared subsequent attacks, once the heavy police patrols were withdrawn.
The bereaved were making funeral arrangements while other residents tried to piece together details of the attack which they intended to present to the police for action.
They included the suggestion that the massacre could have been plotted during meetings landlords had been holding in an hotel in an apparent attempt to ward off future demands for lower rents.
"They feared that the rent problem in Korogocho would spread to this area," said one elder.
He said the violence may have been geared at intimidating tenants to reduce their bargaining power. He dismissed claims that some residents had refused to pay their rent.
Nairobi police chief Geoffrey Muathe had earlier said the rent issue was one theory being pursued by police investigating the killings.
They would also look into whether the violence was politically instigated - as some members of the Opposition claimed yesterday - or whether it was purely criminal.
One elder who has lived in the estate for the last 18 years, Mr George Odanga Adenyo, blamed insecurity for the killings.
"There has been very inadequate security in this area. After nightfall, one would easily be robbed of money and other valuables. The gangsters, were aged between 18 and 25 years and some were known to the local people," he said.
Mr Adenyo added: "They even went to the extent of raping wives and daughters in full view of husbands and fathers, after breaking into houses at night. It was unbearable and it seemed that police were incapable of handling the problem."
That is when elders, especially from the violence-prone Gitathuru area, decided to form a vigilante group, called Taliban, Mr Adenyo said.
He said the Mungiki sect was not to blame and instead pointing his finger at the gangs whose activities had been checked by the vigilante group.
However other residents were categorical that Mungiki was involved. They said they had come to revenge the killing of two of their colleagues, attacked by Taliban members in a 3am fracas on Sunday.
"Mungiki should tell us why they slashed defenceless people in the area, if they had a problem with the Taliban they should have faced us " said Mr Okoth Siasia.
Abalibaho Bar owner Meshack Amauko commented: "People are too afraid of venturing into the night because of Mungiki."
He said the gang attacked his employees and smashed windscreens of his customer's vehicles.
Other residents ,who spoke on condition of anonymity for fear of reprisals, said that the vigilante group had overstepped their jurisdiction.
"Although crime has really gone down, the vigilante group has been harassing people in the name of keeping security. That is the reason why there was the Sunday retaliation," one greengrocer said.
Taliban chairman David Peter Ochieng defended his group, saying: "We have been operating with the full knowledge and in conjunction with the police to stem insecurity in this area. The group, with a membership of about 250, was formed to deal with insecurity in this area. The members are from mixed ethnicity and don't belong to any particular tribe."
He added: "In fact, they are very happy with the job that we are doing. I could say that since this tension began building."
He had called Kasarani police on Sunday to warn them of the impending attack "but they just took it lightly."
"I talked to them in the morning, at 3pm and again at 5pm but they played it down," he said.