Syrian sarin attack survivor describes the feeling of 'a knife made of fire'

One of the victims of a sarin gas attack launched by the Syrian government on its own people in August 2013 compared the effects of the toxin to "a knife made of fire."

Kassem Eid was lucky to survive the bombardment - which killed more than 1,400 civilians, hundreds of them children.

He told "60 Minutes" of the horrors he saw during an incident that the U.N. has called "a crime against humanity."

Forces loyal to Syrian President Bashar al-Assad pounded the Damascus suburbs with the gas rockets in the early morning hours of August 21, 2013, as proved by independent analysis. And a U.N. weapons inspector told "60 Minutes" that the rockets used in the attack were types used by the Syrian Army.

"Within seconds, it just took seconds before I lost my ability to breathe," Eid recalled. "I felt like my chest was set on fire. My eyes were burning like hell. I wasn't able even to scream or to do anything. So I started to beat my chest really hard … to take a breath. 

"Just to be able to take a single breath," he continued. "It was so painful. It felt like somebody was tearing up my chest with a knife made of fire."

WARNING: Graphic images below

The toxic cloud claimed 1,429 lives, according to U.S. intelligence, 425 of them were children. Footage shown by "60 Minutes" showed hundreds of children lying lifeless on the ground, their parents crying over them. 

"Nobody knew what was going on. People were just praying for God to have mercy on them," he told the newsmagazine. "Sir, I've seen things you won't even dream about in your worst nightmares."

Sarin gas is one of the most toxic and fast-acting chemical weapons ever created, according to the Council on Foreign Relations (CFR). It was invented by German scientists in the 1930s and originally meant to be used as a pesticide.

Once inhaled, the toxin attacks both the nervous and respiratory systems, according to CFR. Shortness of breath leads to suffocation, intense pain and seizures. 

All chemical weapons, including sarin gas, are banned under international law. But that has not stopped groups from using it in the past. 

After the attack, Russia brokered a deal in which Assad would give up his sarin stockpiles so that the US wouldn't retaliate against his regime. Assad now uses chlorine barrel bombs to terrorize civilians.