A Somali terror leader implored his fellow countryman in California to send money 'to finance jihad," triggering a chain of events that ended with four convictions.
U.S. government agents recorded dozens of such calls a few years ago, according to the Department of Justice.
And on Friday, a jury found four Somali nationals guilty of supporting terrorism in their native country.
The verdict came after prosecutors played the recordings to jurors in a San Diego federal court during weeks of trial.
The four, who included an imam and a cab driver, had raised $10,000 and wired it to the Islamist terrorist group Al-Shabaab, according to the original indictment.
Cab driver Basaaly Saeed Moalin had many phone conversations with former Al-Shabaab leader Aden Hashi Ayrow, before a U.S. missile strike ended the latter's life in May 2008.
Investigators from the FBI, Homeland Security and a San Diego anti-terror agency recorded dozens of them.
Federal prosecutors filed charges in November 2011. The group pleaded not guilty. But the recordings convinced the jurors otherwise.
The money wasn't coming fast enough for Ayrow, who implored Moalin in at least one recorded call to hurry it up. "You are running late with the stuff," Ayrow told him. "Send some, and something will happen."
Ayrow pushed the cab driver to get his local imam to come up with some funds. Mohamed Mohamed Mohamud ran the City Heights mosque in San Diego, which many in the Somali community attended.
Together with a second cab driver, Ahmed Nasiri Taalil Mohamud, and an employee at a money transfer company, Issa Doreh, they raised the cash and wired it to Al-Shabaab , the Justice Department said.
It wasn't the only favor Moalin did for the terror group.
Moalin had kept a house in Somalia's capital Mogadishu, one of the world's most embattled cities at the time. He offered to let the terrorists use it, the Department of Justice said.
"After you bury your stuff deep in the ground, you would, then, plant trees on top," Moalin told Ayrow in a recorded conversation. Prosecutors argued he was "offering a place to hide weapons."
For months, they talked about "bullets, bombing and Jihad," said U. S. Attorney Laura E. Duffy. After hearing the recordings, the jury no longer bought the defendants' explanation that they "were actually conversations about their charitable efforts for orphans and schools," she said.
Sentencing is scheduled for May 16.
Al-Shabaab is one of about 50 groups that have been designated by the State Department as foreign terrorist organizations.
The Islamist extremists have been waging a war against Somalia's government in an effort to implement a stricter form of Islamic law, or sharia.
In recent years, Somali and African Union troops, who have received funding from the U.S. government, have won many battles against the terror group, pushing it back to a handful of strongholds.
For more than 20 years, Somalia did not have a stable government, and fighting between the rebels and government troops added to the impoverished east African nation's humanitarian crisis.
In January, the United States granted official recognition to the Somali government in Mogadishu.