And as the investigation unfolded over recent months, a name emerged that chilled some in the U.S. government. The Iranian cousin of the man accused of plotting the assassination was Abdul Reza Shahlai, a senior commander in Iran’s Quds Force, who had been linked to the killing of American troops in Iraq.

Shahlai was known as the guiding hand behind an elite group of gunmen from the feared militia of the cleric Moqtada al-Sadr. They had dressed as American and Iraqi soldiers and, in a convoy of white SUVs, stormed a provincial government building in Karbala on Jan. 20, 2007.

Five Americans were killed and three were wounded in the attack, whose brazenness rattled the military. The daring raid became even more notorious after some of the suspected killers were later released by the Iraqi government…

It is unclear how much Shahlai understood about his cousin’s life in the United States and if he understood how unlikely it was that a struggling used-car salesman in Corpus Christi, Tex., could successfully orchestrate a high-profile international plot.