Mohamed Merah had been on the United States' terror watch list for two years before he began the rampage that led to his death Thursday, ending a standoff with police who tried to apprehend the man suspected of killing seven people in France.

Merah, 24, who killed three French paratroopers of North African origin as well as a rabbi and three Jewish schoolchildren in the Toulouse area over several days, is believed to have been placed on the FBI-maintained list in 2010. That year, he was allegedly detained in Afghanistan and sent back to France.

U.S. officials had been gathering information on the French national of Algerian descent long before he launched his killing spree, and Merah was barred from all U.S.-bound flights. There's no record of Merah having been held by either Afghan or U.S. authorities, but he is believed to have traveled to Pakistan and Afghanistan at least once in each of the past three years.

Merah claimed to have al Qaeda training. It is believed he trained with the terrorist group in the Waziristan region of Pakistan, on the border with Afghanistan, according to Agence France-Presse, and he could have traveled to the area as recently as October. 

Pakistan, however, denied Merah had visited the country, and a senior official told AFP: People like Merah use different channels to sneak into Pakistan. These are the kind of channels, which their networks identify as safe and risk-free. 

French authorities said Wednesday that Merah had been detained in Afghanistan on bomb-making charges and linked him to a Taliban prison break in Kandahar in 2010. Police in that Afghan province have denied the report.

French authorities also were aware of Merah, who had a criminal record that included 18 offenses, some of them violent. His two brothers and his mother have been detained for questioning by French police.

There are more than 1 million people on the FBI's terror watch list, according to the American Civil Liberties Union.