By Kate Samuelson
August 23, 2016

Nigeria claimed on Tuesday that its air force had killed a number of senior Boko Haram militants, possibly including the group’s elusive and notorious former leader, Abubakar Shekau.

Government planes attacked the fighters in the village of Taye inside the Sambisa forest in Borno State during a raid on the Islamists’ northeast heartland on Friday night, Reuters reports. Army spokesman Colonel Sani Kukasheka Usman said in a statement that “Their leader, so called ‘Abubakar Shekau,’ is believed to be fatally wounded on his shoulders.”

However, this is at least the fourth time Shekau’s death has been reported. Despite the military declaring him killed in 2009, a man purporting to be Shekau reappeared in videos posted on the Internet less than a year later, when he ridiculed suggestions of his death.

The Boko Haram militant, named among TIME’s 100 Most Influential People in 2015 as the “scourge of Africa,” was reportedly ousted from his leadership position by ISIS chiefs earlier this month. Here’s what we know about him:

Ruthless ideologue

Abubakar Muhammad Shekau is believed to have been born between 1965 and 1975 in Shekau village in Nigeria’s northeastern state of Yobe, according to the BBC. He was a theology student and is fluent in his native Kanuri language, as well as Hausa and Arabic, and appears to understand English too. Shekau has been described as having an “intense ideological commitment and ruthlessness.”

He has demonstrated a bloodthirsty nature, saying in one video, “I enjoy killing anyone that God commands me to kill — the same way that I enjoy killing chickens and rams.”

Journey to becoming a warlord

The jihadist group Boko Haram, whose name translates roughly to “Western education is forbidden,” was founded in 2002 by Mohammed Yusuf. Shekau took over as leader in 2009 after Yusuf was paraded and then executed in front of a crowd by Nigerian security forces, retaliating after 70 Boko Haram fighters attacked a mosque and police station in the town of Bauchi. Shekau is said to have married one of Yusuf’s four wives and adopted their children, following the former leader’s death.

Shekau then began to stage increasingly daring kidnapping and killing raids on schools, police stations, federal institutions, churches and mosques thought by Boko Haram to be violating their interpretation of Islam. Under Shekau’s leadership, Boko Haram has killed some 20,000 people and displaced more than 2 million, according to the International Business Times.

In 2013, the U.S. government’s bounty for Shekau stood at $7 million — $2 million more than what was offered for the Afghan Taliban’s top man, Mullah Omar. He formally pledged allegiance to ISIS’s self-styled caliph Abu Bakr al-Baghdadi in March 2015 and gave ISIS its first franchise in sub-Saharan Africa.

International pariah

The abduction of over 270 schoolgirls in April 2014 brought Boko Haram into the international spotlight, with many using the #BringBackOurGirls hashtag to raise awareness of the campaign to find the abductees. In a series of videos posted online at the time, Shekau admitted to kidnapping the girls and said he would sell them. “I abducted your girls. There is a market for selling humans. Allah says I should sell,” he said, grinning. “He commands me to sell. I will sell women. I sell women,” he added, occasionally laughing throughout the segment.

Some of the abducted Chibok schoolgirls have been killed by Nigerian military air strikes, according to a new video appearing to come from Boko Haram, which shows one kidnap victim pleading for authorities to bow to the extremists’ demands that they release detained militants in return for the girls. It’s not clear how many have died among the 218 who remain missing.

Ousted by ISIS leaders

At the time of his reported death, Shekau had been in a leadership battle with Abu Musab al-Barnawi, who was named by ISIS as the new leader of what it calls its West Africa Province on Aug. 3. An audio speech released the following day, purporting to be from Shekau, criticized his rival and said al-Baghdadi did not respond to letters in which he claimed al-Barnawi is “an infidel” preaching “false creeds.”

According to the Associated Press, Shekau’s speech highlighted ideological differences with al-Barnawi, who has promised to end the attacks on mosques and Muslim markets that had become a hallmark of Boko Haram.

One of many deaths

In 2009, rumors of Shekau’s death by security forces did the rounds in Nigeria — however many believed that the announcement was “merely a ruse, designed to provoke Mr. Shekau into making a public appearance or statement, in the hope of flushing him out,” the New York Times reported. He then appeared in a videotaped interview with a local Nigerian journalist in July 2010, as Boko Haram’s new leader, a position he had held since taking over from Yusuf the year before.

In 2013, an army spokesman announced that Shekau “may have died” between July 25 and Aug. 3 during a shoot-out with security forces. And one year later, the Cameroonian military released photos believed to be of Shekau, suggesting he was killed during a cross-border raid inside Nigeria. At the time, Ryan Cummings, a security analyst, said, “Is this his fourth or fifth death? He dies more often than an iPhone battery,” according to the U.K.’s Times newspaper.

After Shekau’s third death in 2014, theories circulated that the body was that of an impostor. The Washington Post reported that the Nigerian military issued a statement saying a corpse photographed by Cameroon’s military was that of “a doppelganger, masquerading as the leader.”

Tuesday’s statement made no mention of a doppelganger. Only time will tell if this fourth reported death proves to be terminal.

Write to Kate Samuelson at kate.samuelson@time.com.

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