White House outlines evidence to support strike on Syria in memo to Congress members The White House sent a briefing document to Congress members late Friday.

In the moments after President Donald Trump ordered coordinated attacks on chemical weapons facilities in Syria, the White House sent a briefing document to members of Congress prepared by the National Security Council outlining the thinking behind its air strikes.

ABC News obtained a copy of the document, sent to at least one senator, on the evidence that led up to the strikes.

The document outlines six reasons for the attacks launched early Saturday in Syria.

The first point outlines the U.S.'s evidence of a chemical attack on Douma April 7, "killing dozens and severely injuring hundreds of civilians." The document points to a large number of "reliable" photos and videos of victims suffering from the symptoms of a chemical attack. The intelligence points specifically to symptoms of a chlorine and sarin attack on April 7.

ABC News previously reported at least 40 people were killed in the suspected chemical attack.

The document delivered to congressmen cites "credible medical personnel ... including the World Health Organization" treating the effects of a sarin gas attack.

Other evidence cited in the document includes eyewitness accounts of an Mi-8 helicopter launched from Dumayr airfield circling Douma and photos of barrel bombs similar to those previously used by the Syrian government.

The NSC counters arguments made by the Syrian and Russian governments that the April 7 attack was fabricated by Western governments, saying, "Such a widespread fabrication would require a well-organized and compartmented campaign to deceive multiple media outlets while evading our detection."

The document concludes with a demand for the Syrian regime to reveal its chemical weapons program to the Organization for the Prohibition of Chemical Weapons (OPCW) and destroy its remaining stockpiles of chemical weapons -- something the regime claims it already did in 2013 following a U.N. Security Council resolution.

Trump announced the strikes in a press conference at the White House from around 9:30 p.m. The strikes, a joint operation between the U.S., U.K. and France, targeted three locations associated with the production and storage of chemical weapons: a scientific research center; a storage center for sarin and its precursor components; and a chemical weapons storage facility and command post, according to Chairman of the Joint Chiefs of Staff Gen. Joseph Dunford.