The Obama administration is now considering military action in Syria in the aftermath of the chemical attack that killed hundreds and injured thousands of civilians.

The White House said it would release information it has gathered that makes it clear that President Bashar al-Assad was behind the attack. Britain’s Prime Minister David Cameron also claims that evidence points to Assad being the perpetrator, but no western government has yet revealed when the information will be exposed to the public.

Last week, news of a chemical attack sweeping through Ghouta, near eastern Damascus, made headlines and shocked the world. Whether such a ruthless attack was brought about by the Syrian government or by rebel factors was murky and unknown. Though there is still no solid evidence to prove that it was indeed carried out by the Syrian regime, western nations including the UK, France, and the US have all pointed their fingers — and now threats of air strikes — at Assad.

Presenting the evidence and deciding on whether to intervene are what the New York Times today called “the most important public intelligence presentation since February 2003, when Secretary of State Colin L. Powell made a dramatic and detailed case for war…later discredited…about Iraq’s weapons programs." The Obama administration carries a burden of proof; it will have to show how garnering an attack on Syria is in the nation’s best interest.

Doctors Without Borders noted in a press release that it had found 355 people dead from the chemical agent and around 3,000 that seemed to be affected by such a nerve gas, but could not confirm who was behind the attack. The United Nations is currently undergoing an investigation to find out whether a chemical weapon, such as sarin, was used, but may or may not be able to discern who caused the attack. The UN will reportedly be leaving Syria a day earlier than expected, possibly due to the imminent air strikes.

The Council on Foreign Relations (CFR) describes sarin as “one of the world’s most dangerous chemical warfare agents.” It can be absorbed through the skin or inhaled and overwhelms the nervous system, harming muscles and organs. CFR also notes that about one drop of sarin can kill people within minutes if they are not given an antidote. Those who experience a lower dosage of sarin may experience symptoms like nausea, vomiting, and watery eyes.

Tracing sarin is very difficult, terrorism expert Charles Blair told Reuters. In order for chemical experts to confirm what type of gas was used, they would need blood or hair samples from the victims.

The Syrian civil war, which has been raging for two-and-a-half years, has left over 100,000 people dead. This is one of the reasons why New York Times op-ed columnist Nicholas Kristof believes Obama should take a stronger approach in the conflict. “In conjunction with diplomacy, military force can save lives,” Kristof wrote, noting that Assad has slowly crossed a “red line” multiple times to escalate the humanitarian crisis in his country.

But polls show that a large percent of the American population opposes the U.S. meddling with Syrian affairs, fearing that an intervention could turn into a new Iraq war.