DAHYAN, Yemen — Hussein al-Ejri was too excited to sleep on the morning of August 9, so he woke up early in anticipation of the field trip planned for him and about 65 of his Islamic seminary classmates. Hours later, the 11-year-old was one of the few kids on the trip still alive.

That day had started like any other. The group performed early-morning prayer with their teachers and stopped at a busy market near the farming village of Dahyan in northwest Yemen so people could purchase snacks before setting off.

That's where Hussein was when he heard the loud thud of an explosion and saw the bus blown apart.

A few days after the strike, the boy stood atop what was left of the bus and pointed out what was once there.

"One of my friends was sitting here. And another one here, and another there,” Hussein told VICE News. "They were all injured. After the explosion, I found one of my friends killed here but couldn't find the rest of my friends, just this one.”

Of the 54 people killed in that attack, 45 of them were children between the ages of 6 and 15. Hours later, Saudi coalition spokesman Col. Turki al-Maliki said on TV that the strike was made in retaliation against a Houthi rebel militia missile attack on the Saudi-Yemeni border the night before, telling Al-Arabiya that Houthi “operatives” were aboard alongside the children.

In a subsequent internal investigation, the Saudi government ultimately concluded that the “timing” of the strike was a mistake.

But since 2015, the Saudi-Emirati coalition has been waging a brutal campaign against the Iranian-backed Houthi rebels in an effort to curb Iran's creeping influence in the Arabian Gulf. In the process, they’ve launched more than 18,000 airstrikes, at least a third of which have hit civilian targets, according to the Yemen Data Project. Many of them, including the Dahyan airstrike, used American-made weapons: at least 13 so far, according to documentation from the Yemeni human rights group Mwatana.

At the Dahyan airstrike, witnesses found remnants of a MK 82 Lockheed Martin bomb, probably made at a factory just outside of Scranton, Pennsylvania. The discovery of American bomb fragments at airstrike sites in Yemen has become fairly common, fueling public anger at not only the Saudi-Emirati coalition but also its main weapons supplier, the United States. In a rare show of bipartisan accordance, the U.S. has so far agreed to sell more than $110 billion worth of weapons to Saudi Arabia in proposals reached under both the Obama and Trump administrations.

But it’s not just weapons Saudi Arabia buys from America. The U.S. has also provided the coalition with intelligence, mid-air refueling and even Green Berets to assist on the border.

Even so, the news of American involvement in the killing failed to make a splash for months — that is, until the high-profile murder of journalist Jamal Khashoggi prompted American politicians to reexamine their role in the Saudis' efforts.

This segment originally aired November 20, 2018 on VICE News Tonight on HBO.