Last month, grainy photograph attributed to Cameroonian authorities began to circulate online that appeared to show Abubakar Shekau, leader of the Nigerian group Boko Haram, lying dead from a gunshot wound. If the photo was accurate, it would appear to have been a major blow to the Islamist extremist group, which gained worldwide infamy with the kidnapping of more than 200 schoolgirls in April.

Among those who knew Boko Haram well, however, there was significant skepticism. There had been reports of Shekau's death at least twice before, and both times he had resurfaced, apparently very much alive. "I have it on authority that Shekau is well & alive," Nigerian journalist Ahmad Salkida tweeted after the news came out, "the picture going round is NOT the person who torments us with his group."

On Thursday, the news service Agence France-Presse (AFP) said it had obtained a video from Boko Haram that featured a man who appeared to be Shekau. "Here I am, alive," the man said. "I will only die the day Allah takes my breath."

Boko Haram's mysterious leader appears to have pulled off his reappearing trick yet again.

Shekau's "death" and reappearance show just how difficult a figure he is to understand. As my colleague Terrence McCoy has noted, Shekau may lead one of the world's most notorious extremist groups and have a $7 million bounty on his head, but basic facts about his life (for example, his age) are hard to ascertain.

Stranger still, analysts believe that there may be more than one person posing as "Abubakar Shekau." In one analysis, the Terrorism Research & Analysis Consortium looked at different videos released by Boko Haram and found significant inconsistencies in "Shekau."

"Even though the mannerisms and facial hair are similar in each of the videos below, in some cases he appears much heavier or much darker in skin color, and the posturing is very different between each man," the analysis noted. "The cadence of each speaker varies dramatically and each speaker opens his mouth very differently."

As the Shekau image began to spread, Nigeria suggested that the man pictured was an impostor and that the original Shekau was dead. In the course of fighting last month in the town of Konduga, near the Cameroon border, "one Mohammed Bashir, who has been acting or posing on videos as the deceased Abubakar Shekau ... known as leader of the group, died," Defense Ministry spokesman Maj. Gen. Chris Olukolade said, according to the news agency Reuters.

It is not clear when or where this new video was filmed, or who is actually in it. "As far as we are concerned, the individual who was appearing in video and claiming to be the leader of the terrorist group was killed in the Kondunga battle in September," Nigeria's military said in a statement. "The resemblance of the corpse and that of the eccentric character was incontrovertible. His identity was equally corroborated by people who knew him before we announced his death."

Regardless, the new video may distract from a bigger problem. The repeated "death" and "rebirth" of Shekau has already added to the mystique surrounding him and the group he leads, and many believe that Boko Haram has more momentum than can be derailed by his death at this moment (the group survived the death of founder Mohammed Yusuf in 2009, for example).

The global attention that followed Boko Haram's April kidnapping has since faded, and the group seems to have had a recent territorial resurgence. It's believed that the group is aiming to set up an Islamic caliphate in the areas it controls.

Boko Haram "is rapidly gaining ground in Africa," J. Peter Pham, director of the Africa Center at the Atlantic Council, wrote last month, "achieving many of the same operational and strategic successes that have made [the extremist group Islamic State] such a force to be reckoned with, including significant dominion over territory and populations."

In the 36-minute video obtained by AFP, Boko Haram brags about its power, showing the wreckage of a Nigerian air force jet it claims to have shot down and airs footage that appears to show it has implemented strict sharia law in parts of Nigeria (one scene shows a man being stoned to death for adultery, according to AFP).

"Nothing will kill me until my days are over... I'm still alive," the man said to be Shekau says. "Some people asked you if Shekau has two souls. No, I have one soul, by Allah."

Correction: This post has been updated to make clear that the image of that claimed to show Shekau dead did not officially come from the Cameroonian military.