After Saturday’s attack on Douma, the White Helmets posted graphic images and videos on Twitter of the impact of the alleged attack on civilians in Douma. It said more than 40 people, including children, were killed and dozens wounded, adding the death toll was likely to increase. It said civilians had suffocated after Assad’s aerial bombardment of the area.

The use of chemical weapons is prohibited under international treaties—pacts to which Syria is a signatory. While the graphic nature of the attacks is incontestable, the fact remains that the Assad regime has caused widespread devastation using conventional weapons in the Syrian civil war that began in March 2011: More than 500,000 people have been killed, the war has created more than 5 million Syrian refugees, and entire cities have been flattened.

Douma is the last rebel redoubt in Eastern Ghouta, the area outside Damascus that Assad continued to bomb despite a 30-day, UN-mandated ceasefire that went into effect in February and lapsed the following month. More than 1,000 civilians have been killed in Eastern Ghouta and the rebels have been pushed out of most of the area, save for Douma, the town that was struck Saturday.

President Obama famously said the use of chemical weapons were a “red line” for the United States in the Syrian conflict. But when Assad used sarin against civilians in August 2013, Obama instead worked with Russia on a deal to destroy Syria’s chemical weapons stockpile. The strength of that agreement became apparent when Assad used chemical weapons after the deal went into effect. If Obama’s apparent lack of action emboldened the Syrian regime, it is not clear if Trump’s military strikes in April 2017 after Assad employed sarin gas again had any impact, either. The regime has been accused of using chlorine against civilians on several occasions after that—most recently on Saturday.

The attack—and what the White House will do next—is further complicated by the fact the Trump administration’s policy toward Syria appears muddled. Last week, the White House said the U.S. military’s mission in Syria “to eradicate ISIS … is coming to a rapid end.” That statement, which was attributed to the White House press secretary, did not set a timetable for a withdrawal of the approximately 2,000 U.S. troops in Syria. But news reports indicated that Trump, who two weeks ago said the United States would leave Syria “very soon,” was unhappy with the U.S. military’s continued presence in the country and wanted troops out within six months. Trump’s tweets on Sunday might signal another policy shift on Syria. When and whether that’ll occur is anybody’s guess.