A chemical attack in an opposition-held town in northern Syria killed dozens of people Tuesday and left others gasping for air and convulsing in the streets.
The Britain-based Syrian Observatory for Human Rights said at least 58 people died, including 11 children, in the early morning attack in the town of Khan Sheikhoun.
The Trump administration blamed Syrian government for the attacks but also said Syria's patrons, Russia and Iran, hold "great moral responsibility" for the deaths.
Witnesses said was the chemical attack was carried out by fighter jets operated by the Russian and Syrian governments.
In a statement, the Syrian government rejected claims that it was responsible, saying it does not possess chemical weapons, hasn't used them in the past and will not use them in the future. The Russian Defense Ministry also denied involvement.
In response to the chemical attacks, the U.S. issued a missile attack on Syria.
Experts suspect the chemicals were a mix of gases including Sarin.
But what exactly is Sarin?
Sarin gas is an odorless, colorless liquid used as a chemical weapon because of it's effects on the nervous system. Sarin can be fired from a rocket or bomb aerially or released from the ground. It's generally considered a weapon of mass destruction and when fired off, the liquid disperses as an aerosol.
It was first manufactured in 1938 by scientists in Nazi Germany, who were working on pesticides and stumbled across the lethal poison. It was never used until former Iraqi dictator Saddam Hussein, who was executed in 2006, perpetrated the largest and first confirmed sarin gas attack to date in 1987.
What does it do to your body?
Within the nervous system, there are chemical messengers called neurotransmitters that are in charge of stimulating muscles. Once stimulated for reaction, there's an enzyme that eats up and clears the excess chemical to start the process again.
Sarin gas gets in the way of this enzyme and disrupts the nervous system.
"What happens is that nerve is constantly stimulated and the glands are over-stimulated, that's why you see nausea, vomiting and you lose muscle control because you're getting over-stimulated and once it affects the diaphragm that's when you stop breathing and people die." said Dr. Pawan Grover, a pain interventional specialist known for his humanitarian efforts.
A person can also become paralyzed, experience convulsions, start vomiting and lose control of their bowels, tear ducts, virtually any function the nervous system touches.
What's the best thing to do if you're attacked with Sarin gas?
Sarin gas is heavier than air so settles low to the ground, according to Grover.
To lower risk of heavy exposure, its best to try to reach higher ground.
"The other thing is, it sticks to your clothes," Grover explained.
Taking or ripping off clothing reduces exposure which is why many images of the recent chemical attack in Syria show people with little clothing on.
One of the ways to immediately take action against Sarin exposure is to wash it off the skin if possible. Once help has arrived, Sarin can be treated with a medication called atropine which reverses the effects of Sarin.
Until then, breathing must be controlled. Extra oxygen doesn't help because of the over-stimulation the body is experiencing.
Even emergency workers or people not immediately exposed to sarin can feel symptoms if they touch victims with their hands or without using special masks. It may take a couple hours but it's still a risk.
Is Sarin gas always deadly?
Not always. It depends on how much you get exposed to the chemical.
"If you get mild exposure, you'll have mild symptoms." said Grover. "If you get really, a lot of exposure you can die within ten minutes."
Fortunately, Sarin gas disperses quickly and the doesn't have as strong effects as it furthers away from the source.
"Historically, the reason why they inject Sarin or released Sarin, is then it disperses and the military can come in and take over that area," said Grover.
Are the effects long term for survivors?
"There are long term effects," said Grover. "It can persist and cause all sorts of things. That's why chemical weapons are banned because it's a pretty horrible issue."
Sarin has been known to cause severe brain damage as well as respiratory and muscle damage long after exposure.