The attack on a prison van in northern France that left two guards dead and three wounded began at 10:57 am (0857 GMT) and lasted just two minutes.
A black Peugeot SUV rammed the vehicle as it emerged, lights flashing and followed by a second prison service car, from the motorway toll gate at Incarville, just south of Normandy capital Rouen.
Out of the ramming car, "stolen a few days before" according to top Paris prosecutor Laure Beccuau, surged hooded attackers in black armed with military-style weapons.
The vehicle "had halted on the verge, waiting for the convoy" to pass the toll, Beccuau added, in a sign of an attack prepared down to the last detail.
CCTV images from the scene viewed by AFP show the beginning of the assault on the prison van, although a passing truck obscures some details.
More assailants can be seen arriving from behind the convoy, with prosecutors saying they jumped out of a white Audi car.
The prisoner, Mohamed Amra, was being escorted that day by five guards -- a "level three" protection that is the second-highest available for inmate transport in France, reserved for those implicated in terror or organised crime cases.
Guards were "of course armed", Beccuau said, adding that "initial findings from the scene lead us to think that some may have used their service weapons".
But the team had on them only "a basic Sig Sauer (automatic pistol) against military weapons," said Frederic Liakhoff, a representative for the FO union at the prison in the northern city of Caen where Amra was being transported.
'Very, very loud'
With their "long weapons" (rifles), the attackers "fired multiple times on the two prison service vehicles, killing two agents and wounding three others," Beccuau said.
It was the first time a French prison guard had been killed in the line of duty since 1992.
Meanwhile the life of one of the three men injured remains in danger.
There were "loud gunshots, very, very loud," said Jerome Barbier, who was on his way to tend his beehives near the Incarville toll station when the attack happened.
"After that, there was a pause for one or two minutes, a big blast, two gunshots and then it was all over," the local resident told AFP.
One minute and 40 seconds into the attack, the surveillance video shows a man -- apparently a guard -- being forced towards the prison van at gunpoint.
Instants later, a man wearing white trainers climbs out.
He and five black-clad accomplices flee before an explosion.
Later Tuesday, "two vehicles were found burned out" not far from the scene, Beccuau said.
"The crime scene reveals the extreme violence the criminals we are hunting for perpetrated," she added after visiting the site.
"The resolve of judges and investigators will rise to the challenge of this violence."
Interior Minister Gerald Darmanin told broadcaster RTL that "considerable" resources had been deployed to find escapee Amra and the "gang who freed him in deplorable circumstances".
"More than 450 police and gendarmes" were in the field Tuesday in the Eure department where the attack took place, he added, saying France had also called in "international cooperation".
(This story has not been edited by NDTV staff and is auto-generated from a syndicated feed.)
