PARIS (AP) — A former French intelligence chief said Thursday he believes that attacker Mohammed Merah acted alone during his 2012 shooting rampage that saw seven people killed but that he received outside help during his preparations.

Bernard Squarcini told a court in Paris that Merah, who was killed days after the attacks at a Jewish school and against French soldiers, was radicalized by extremist networks in France and abroad.

"He acted alone for more efficiency and to make sure he would not leave traces behind him," Squarcini said at the trial of Merah's older brother, Abdelkader Merah. "Mohammed Merah acted alone, but other people were holding his hand."

Prosecutors believe Abdelkader Merah played an active role in radicalizing his brother and in plotting the attacks. If convicted of complicity to terror, Abdelkader Merah faces a maximum sentence of life in prison.

In March 2012, Mohammed Merah killed three French paratroopers in Toulouse and Montauban, in southern France. Then a few days later, he burst into a Jewish school, killed a rabbi and his two young sons and grabbed an 8-year-old girl and shot her in the head.

Squarcini headed the French police counterterrorism agency when Merah killed three French paratroopers, three Jewish schoolchildren and a rabbi.

At the time, Squarcini said Merah acted alone without any affiliation to any extremist network. He said Merah had been self-radicalized when in prison for petty crimes.

He appeared to backtrack slightly Thursday, telling the court he had limited information about Merah's connections at the time of the killings.

Merah had been on a register of people suspected of being radicalized in 2006 because of his relationship with older brother Abdelkader Merah, who is on trial for complicity to terror in connection with the three shooting attacks in and near Toulouse.

Mohammed Merah had also been on the U.S. government no-fly list. In 2010, French military intelligence had been alerted by U. S. officials after he turned up in southern Afghanistan and was caught at a random roadway checkpoint by Afghan police before being handed over to the U.S. military.

He was also quizzed by police when he returned from Pakistan, where he met with an Al-Qaeda affiliated cell.

"Before the facts (the attacks), the Merah files had not been considered a priority," Squarcini told the court.

The 23-year-old Merah died days after the killings, following a 32-hour standoff with France's police special forces.

Questions immediately arose about the slow police response to the attacks. Squarcini said authorities couldn't have foreseen the attack at the Ozar Hatorah Jewish school because Merah planned it at the last minute.

Meanwhile, two persons arrested on the sidelines of the proceedings were released without charge Thursday.