According to the records, communications by Larossi Abballa in 2011 "highlight the fact that he seemed also a volunteer to commit violent actions in France," in addition to wanting to be a jihadist fighter overseas.
Abballa declared his allegiance to ISIS in a video message he recorded Monday after taking over the couple's home in Magnanville, west of Paris. Following a standoff with police, Abballa was shot dead by a SWAT team and the couple's 3-year-old son, who had been held by the attacker, was rescued.
Given Abballa's record, and the fact that he was recently placed under investigation for alleged involvement in a jihadist recruiting cell for Syria, many in France are asking why he was not under more intense surveillance, or even house arrest.
From petty criminal to jihadist killer
Abballa fits in many ways the typical profile of the would-be jihadist. Before his arrest in 2011, he had fallen into a life of petty crime. He began hanging out with a half-dozen men who downloaded everything from jihadist sermons to bomb-making manuals.
They did physical training, and even practiced beheading techniques on rabbits in woods near Paris, according to court documents. And they raised money to send would-be jihadists to Pakistan.
But two men they sent, at the beginning of 2011, were arrested in Lahore and returned to France. Investigators then uncovered the rest of the cell, arresting Abballa and seven others.
The former judge who questioned Abballa, Marc Trevidic, told the French daily Le Figaro that the charges against him in 2011 were tenuous. "There was not much that we could hold against him," Trevidic is quoted as saying.
'Thirst for blood'
The court documents show Abballa as a follower rather than a leader in the cell, but impatient to wage jihad somewhere: Pakistan, Tunisia or -- even better -- France itself.
On February 19th 2011, he wrote to a co-conspirator: "Allah with his willingness will give us the means to hoist the flag here; nothing is done, it's a challenge to meet."
Subsequently he wrote of the "need to start work...the cleansing of the infidels....I have a thirst for blood."
Others in the group saw Abballa as "bizarre" or "mysterious," according to the documents; his knowledge of Islam was sketchy.
But while awaiting trial, he became known in prison for his militant proselytizing -- which led him to be moved between four different jails.
He ultimately received a three-year sentence in September 2013 for association with known terrorists - but was released immediately for time served. He'd been in jail for 27 months. Abballa remained on the official list of individuals suspected of being linked to terrorism -- the Fiche de Surveillance -- and was on probation for six months.
Abballa appeared to have turned a corner after his release from prison. He set up a food delivery business; a former girlfriend says it seemed he had changed for the better.
But he hadn't. In February this year Abballa was placed under investigation in connection with recruiting fighters for Syria. He wasn't, however, arrested.
Referring to other recent cases of homegrown jihadists striking on French soil, the conservative daily Le Figaro commented that "(w)hat is most incredible is that like (Toulouse gunman Mohammed) Merah
, like Coulibaly, like the Kouachi brothers... Laroussi Abballa escaped the vigilance of authorities."
Three others detained
Since Abballa's rampage on Monday, three men associated with him have been detained. They are still being questioned, according to French officials.
One of them is Aberouz Charaf-Din, regarded as a leading member of the 2011 cell. Charaf-Din was sentenced to five years but according to his attorney released in 2014 or 2015.
The government has rejected suggestions that it missed signals about Abballa's intentions.
"This man, who became a monster the moment he killed, had shown no signs of preparation," said Justice Minister Jean-Jacques Urvoas.
And that goes to the heart of the dilemma for the French authorities, like their counterparts in the US and elsewhere.
"In France, we judge not on intentions but deeds," Urvoas said. And it is beyond the government's capability, or even will, to monitor the approximately 14,000 names on the security services' lists of radicalized individuals.
Security vs. civil liberties
Some conservatives in France are arguing for a form of preventive detention for those regarded as most dangerous, that would extend existing police powers to keep people under house arrest.
Eric Ciotti, a right-wing parliamentary deputy, says he has frequently proposed detention centers for about 1,000 suspects. The Council of State, which advises the government on legal issues, has rejected the idea as unconstitutional.
And even if such centers were introduced, what's to say that another Larossi Abballa would not be seen as among the most dangerous, until his intentions became deeds?
In the chilling video he recorded while at the couple's house, Abballa urged ISIS sympathizers to attack police, prison officers or town officials.
"It's super simple," he said: "Just wait for them outside their offices."
It's a form of terrorism that needs no wider network, nor contacts with ISIS, nor the purchase of heavy weapons. As one official noted Thursday, the opportunities for such attacks are infinite.