WASHINGTON (AP) — A former Blackwater security contractor has been convicted of murder at his third trial in the 2007 shooting of unarmed civilians in Iraq.

Nicholas Slatten, of Sparta, Tennessee, was found guilty of first-degree murder Wednesday in Washington.

Prosecutors say Slatten was the first to fire shots in the killings of 14 Iraqi civilians at a crowded traffic circle in Baghdad. The shooting strained relations with Iraq and drew intense scrutiny of the role of American contractors in the Iraq War.

The defense had argued that Slatten opened fire because he thought a bomb-laden car was headed toward his convoy.

An appeals court had overturned his 2014 conviction, saying he should have been tried separately from three other men. A jury couldn’t reach a verdict in his second trial last summer.