Mohammed Merah, the man suspected of the Toulouse killings, had been on a French security service "watch list" since 2008. He and his older brother, Abdelkader, have been on a list of possible suspects since the first in a series of three attacks and seven killings in eight days.
Mr Merah was arrested by US authorities in Afghanistan in 2008 and sent home to France.
He belonged to a small, extremist Islamist group, run by his brother, and regarded by security services as harmless.
In the past four years, he twice applied to join the French army but was refused because of minor offences.