There is a drug found almost exclusively in the Middle East, used by IS fighters that masks pain, fear, hunger, and keeps fighters awake, calm and alert for long periods.
A survivor of the Paris terror attacks said "I saw a man who was peaceful, composed, with a face that was almost serene and contemplative, advance towards the bar.....he sprayed the terrace with bullets as anyone else would spray their lawn with a garden hose."
Seifeddine Rezgui, the Tunisian man who killed 38 people on a beach at Sousse in June 2015 was also thought to have taken a drug before the shooting.
So where does their courage come from?
It's called Captagon, a synthetic amphetamine-based pill and the French believe the Jihadists took it to prepare themselves hours before the November 13 massacre.
Captagon was originally produced in the West in the 1960s to treat hyperactivity and depression but was later banned because it was too addictive. But today, it's being overwhelmingly used in the Middle East, particularly in Syria, where it's manufactured and generates millions of dollars to buy more weapons.
A drug control officer in the city of Homs told Reuters he had seen the effects of Captagon first hand on captured prisoners. "We would beat them and they wouldn't feel any pain...many would laugh while we were dealing them heavy blows....so we would leave them for about 48 hours until the effects of the drug wore off."
A Saudi prince was arrested at Beirut airport, accused of trying to smuggle two tonnes of Captagon pills on his private jet. He is accused of transporting the drug to sell to militant groups in Syria.
Hezbollah, the Lebanon-based Shiite group is also involved with the manufacture and supply Captagon which supplies more than enough money to finance their needs. They have also strengthened their co-operation with Syrian, Lebanese, Saudi and Palestinian drug dealers.
So now we know. This magic pill takes away all emotion and allows the recipient to carry out unspeakable acts, without the slightest hint of compassion or remorse.