Al-Jazeera on Tuesday decided not to air a video that seems to have been filmed from the killer's point of view and includes the cries of his victims. The decision came after President Nicolas Sarkozy asked the network not to broadcast it.
While French politicians describe gunman Mohamed Merah as a "lone wolf" terrorist, his brother is behind bars on suspicion of helping in the attacks and police are continuing to look for potential accomplices.
A French official close to the investigation said the video was not sent by Merah, a 23-year-old Frenchman who was killed in a shootout Thursday after a 32-hour standoff with police at his apartment building in Toulouse.
Another official said the envelope sent to Al-Jazeera contained a Wednesday postmark from a large postal processing centre for the area around Toulouse, meaning it was unclear exactly where it was mailed from. He could not say anything about who may have sent the video.
The first official said a technical analysis had concluded that it was not sent by Merah but did not indicate whether that analysis included fingerprints, DNA, surveillance or other data.
The two officials spoke on condition of anonymity because of the sensitivity of the case.
Merah was in his apartment, surrounded by police, from well before dawn Wednesday until he was killed Thursday morning. Police did not elaborate on why they think he did not put the package into the mail before then.
Prosecutors have said that Merah filmed all of his attacks, which began March 11 with the murder of a French soldier. Before the spree ended, two more soldiers and three Jewish children and a rabbi were killed, while another student and another paratrooper were wounded.
Police said Merah claimed the attacks and had told them he had links to al-Qaida, travelled to Afghanistan and received weapons training in the militant-riddled Pakistani tribal region of Waziristan.
French intelligence officials say they have found no sign of a link between Merah and al-Qaida or other international terrorist networks. Still, investigators say they are open to the possibility of accomplices.
Preliminary charges for complicity in murder and terrorism have been filed against Merah's older brother, Abdelkader, though no evidence has emerged that he took part directly in the shooting.
It was not clear if Abdelkader could have sent the video. Police say they first detained him as they carried out Wednesday's early morning raid.
"What we know is that it (the video) was reassembled. Things were added in. We don't know if the full sequence was in it. But it was not just the video as it was filmed. There was an editing process and additions made," the first official said.
Zied Tarrouche, Al-Jazeera's Paris bureau chief, said the video had clearly been edited, with religious songs and recitations of Quranic verses laid over the footage.
The footage appeared to have been taken from the point of view of the killer, perhaps from a camera hung around his neck, according Tarrouche, who described the video to BFM television station. He said they were a bit shaky but of a high technical quality.
"You can hear gunshots at the moment of the killings. You can hear the voice of this person who has committed these assassinations. You can hear also the cries of the victims, and the voices were distorted," Tarrouche said.
The footage was contained on a USB key sent with a letter to the Paris office of the Qatar-based television company, Tarrouche said. The letter, written in poor French with spelling and grammar errors, claimed the shootings were carried out in the name of al-Qaida. The second official said it was hand written in all capital letters.
The channel said the video was received from an anonymous source on Monday and immediately passed it on to French police.
"In accordance with Al Jazeera's Code of Ethics, given the video does not add any information that is not already in the public domain, its news channels will not be broadcasting any of its contents," the broadcaster said in a statement.
Al-Jazeera said it had received many requests by media to look at the video but it would deny all of them.
That decision came after Sarkozy, other French officials and family members of the victims had asked that it not be broadcast.
Tarrouche said the Paris prosecutor, whose office is leading the investigation, had also called to explain the consequences of disseminating the images. But Tarrouche said the prosecutor said he would not prohibit the channel from "doing its work as journalists."
Al-Jazeera was frequently used early in the Iraq and Afghan wars as a conduit for militants, including Osama bin Laden, to distribute taped statements. As the Iraq war progressed, many of these tapes included gruesome killings and beheadings of Western or foreign hostages, although the station edited out some of the grisliest scenes at the moment of death.
The broadcasts drew outrage, especially from the U.S. government. Over time, most militant groups opted instead for posting such videos on their own websites, where they were not subject to outside editing.
Meanwhile, Merah's father, who was estranged from his son and lives in Algeria, asked why a "strong country" like France killed his son instead of capturing him.
"Why did they kill him? ... They could have used gas, for example to take him like a baby," Mohamed Benalel Merah asked in an interview aired Tuesday by France 24 TV. The father said his son should have been taken alive and judged.
Sarkozy, in the middle of a tough re-election campaign, has announced a raft of new measures aimed at preventing the spread and incubation of radical ideas, including penalizing those who regularly consult websites that promote jihad.
On Tuesday, he said wanted to speed up the process of expelling radicals from France as well as prevent them from ever entering.
"Extremists are playing with our administrative formalities. Our job is to be more efficient," he said. "Preachers who continually target our system can stay where they are. We don't want them on the soil of the French Republic."
Meanwhile, another brother, Abdelghani, told a religious representative that the family wants Mohamed Merah's body to be buried in Algeria.
The funeral home was to make the request Tuesday with the Algerian consulate, and the body would be transferred Thursday if the authorization is granted, Abdallah Zekri, a representative of the Paris Mosque in charge of Toulouse.
Abdelghani Merah initially wanted the body buried in France, but insisted he would not attend any funeral of his younger brother, "who he considers a monster," according to Zekri.
Ultimately the brother gave in to his mother's wishes, Zekri said.
Associated Press writer Sylvie Corbet in Paris contributed to this story.