NAIROBI, Kenya (AP) -- Tugging on his winter hat, the Islamic militant leader declared with a sneer: "I will sell women."
His name is Abubakar Shekau, commander of Nigeria's most feared terror group, Boko Haram. His threat to sell nearly 300 teenage school girls abducted from a school in remote northeast Nigeria came in a grainy video released this week.
The warning has vaulted the wanted terror leader into global headlines.
Even before the April 15 kidnapping, the U.S. government was offering up to a $7 million reward for information leading to the arrest of Shekau, whom the U.S. has labeled a specially designated global terrorist.
"He's isolated, he's increasingly extremist and he's delusional enough to think he could bring down the Nigerian state," said J. Peter Pham, the director of the Africa Center at the Washington-based Atlantic Council, who wrote a 2012 report called "Boko Haram's Evolving Threat."
In lectures heard in scratchy recordings, Shekau says that holy war is the only way to bring change for Muslims in Nigeria as he urges his followers to carry out assassinations and bombings in the oil-rich nation of more than 160 million. The country has a predominantly Christian south and a Muslim north.
Pham says the group has grown increasingly violent.
Boko Haram's original leader, Mohammed Yusuf, tried to establish an Islamic state in northern Nigeria by non-violent means. After Yusuf's 2009 death, Shekau took the opposite approach.
In his breakout jihadi video, Shekau wore a headdress and was framed by an AK-47 assault rifle and a stack of religious books. He proclaimed himself the head of Boko Haram and said: "Do not think jihad is over. Rather, jihad has just begun."
Shekau surfaced in 2010, the same year al-Qaida in the Islamic Maghreb took in members of Boko Haram who had traveled to southern Somalia to train in militant camps run by the terror group al-Shabab. Violent jihad is seen as a legitimate expression of Islam in Shekau's militant Salafist world view.
Since Shekau's takeover of Boko Haram - the name means "Western education is sinful" - more than 4,000 people have been killed, nearly 500,000 displaced and hundreds of schools and government buildings destroyed, according to International Crisis Group.
Boko Haram's first lethal operation against Western interests came in August 2011, when a car bomb targeted the U.N. headquarters in the Nigerian capital, Abuja, killing some two dozen people.
Like many other terrorist leaders, Shekau issues a steady drumbeat of jihadi videos. He has threatened President Barack Obama in at least three of them, though analysts say the group poses no threat to U.S. interests.
In spring 2013, Nigerian President Goodluck Jonathan declared an emergency in three Nigerian states and deployed additional troops that have driven Boko Haram from most larger cities and towns.
Shekau was not considered to be Yusuf's natural successor, said E.J. Hogendoorn, a top Africa expert at the International Crisis Group. He called Shekau Yusuf's muscle.
"But because he's fairly ruthless he was able to take over command of the group and so he kind of has emerged from being a local leader to a regional threat," Hogendoorn said.
Shekau's threats against the school girls have earned him global headlines and brought in offers of assistance from Britain and the U.S., which the Nigerian government has accepted. Until now, Nigeria had been reluctant to accept foreign help in the fight against Boko Haram, Pham said.
That likely means that while the kidnappings have raised Shekau's profile, he probably doesn't have to worry about a drone strike targeting him in the near future, Pham said.
In the video in which he threatened to sell the kidnapped school girls, Shekau growled and displayed what appeared to be nervous tics, grabbing at his pants and his hat. That's consistent with past videos.
"He has a reputation for being very erratic, very fiery," Hogendoorn said.