Mohammed Yusuf, leader of an Islamic sect which launched deadly raids across northern Nigeria, has died in police custody, officially as he was trying to escape.
His followers attacked several police stations, threatening to overthrow the government and impose strict Islamic law - but who exactly are the group known locally as the Taliban?
Since the group emerged in 2004 they have become known as "Taliban", although they appear to have no links to the Taliban in Afghanistan.
Some analysts believe they took inspiration from the radical Afghans, others say the name is more a term of ridicule used by people in Maiduguri, the city where they were founded.
The group is also referred to as Boko Haram, which means "Western education is a sin" - one of their core beliefs.
Isa Sanusi, from the BBC's Hausa service, says the group has no specific name for itself, just many names attributed to it by local people.
If their name is uncertain, however, their mission appears clear enough: to overthrow the Nigerian state, impose an extreme interpretation of Islamic law and abolish what they term "Western-style education".
In an interview with the BBC before he was killed, Mr Yusuf, 39, said such education "spoils the belief in one God".
"There are prominent Islamic preachers who have seen and understood that the present Western-style education is mixed with issues that run contrary to our beliefs in Islam," he said.
"Like rain. We believe it is a creation of God rather than an evaporation caused by the sun that condenses and becomes rain.
"Like saying the world is a sphere. If it runs contrary to the teachings of Allah, we reject it. We also reject the theory of Darwinism."
Mr Yusuf himself was something of an enigma.
Analysts say he was extremely wealthy and highly educated.
"He is graduate educated and very proficient in English," says Nigerian academic Hussain Zakaria.
"He lives lavishly - people say he drives a Mercedes Benz. And he is very well-educated in a Western context."
'We could see it coming'
Despite the secrecy surrounding the group, many in Nigeria say the attacks were far from surprising.
Mannir Dan Ali, a journalist with Abuja-based Trust newspapers, says there was a minor incident in early June which appeared to spark a series of statements from the group threatening reprisals.
"The whole situation seems to be a failure of intelligence, a failure of the security forces to act before matters reached the point that they have now reached," he says.
"We could literally see it coming over the past few weeks."
There has been widespread criticism of the security forces for their perceived laxness in monitoring the group.
Boko Haram's members are largely drawn from disaffected youth - university students and jobless graduates among them.
Aminu Abubakar, a journalist covering the area for the AFP news agency, says it is widely believed that the authorities have been reluctant to deal with the militants because some of them come from rich families with connections to the government.
"People believe the government didn't want to crack down on these people because their parents would get angry," he says.
"But now it is becoming a monster, the government has realised it has made a mistake and the earlier they deal with these people, the better."
No 'swelling of ranks'
Divisions remain on how much of a threat the group poses - and how to deal with it.
Information ministry spokesman Sunday Dare says support for the militants' cause is waning.
"We live in a country where people are quite educated and I guess people are happy to make their decisions about Western education or otherwise and how it corrupts their values," he says.
"I don't see a swelling in their ranks at all."
And Patrick Wilmot, a former lecturer at Jos university, said mainstream Muslims look on the so-called Taliban as "crazy".
"They don't need to be taken that seriously, they just need to be monitored."
The BBC's Caroline Duffield, in Lagos, says the group's member have isolated themselves from the rest of the community.
She says there have been incidents where local groups have prevented them from meeting in mosques and there is very little support for their stance in the wider community.
But the upsurge in violence has caused real alarm throughout Nigeria.
More than 300 people - mostly militants - were killed as a wave of unrest spread from the city of Bauchi on Sunday through Borno, Yobe and Kano states the following day.
And while Mr Yusuf's death will obviously weaken the group, it could also spark calls for revenge attacks from those of his followers who have survived this deadly week.