The FBI offered a $50,000 reward this week for information leading to the arrest of a US citizen wanted on terrorism charges.
The suspect is Ahmad Abousamra, who fled his home in Massachusetts in 2006.
He's known to be an associate of Tarek Mehanna, another Massachusetts resident, who was jailed in April for 17 years.
Mehanna was convicted of providing material support to terrorists and conspiracy to kill in a foreign country.
Abousamra was indicted on the same charges in 2009; what's new in the story is the reward, and the FBI's appeal to the public here, and around the world, for information.
Richard DesLauriers, the special agent in charge of the FBI's Boston Division, says the FBI has embraced social media in recent years.
"This considerably broadens our reach across the world stage," says DesLauriers. "Really, our reach overseas, in the past, using traditional media, had been limited."
You can now message tips directly to the FBI on Facebook or Twitter.
Abousamra was last known to be in Aleppo, Syria. He was born in France, but is of Syrian descent, and had extended family in Aleppo.
Some activists have expressed concern over the case of Mehanna and Abousamra. Prosecutors in the Mehanna trial said the pair couldn't even locate the terrorist training camps in Pakistan or Yemen. Other reports say they were rejected by al-Qaeda.
But the FBI's DesLauriers insists the case is extremely serious, as both men traveled with the clear intent of wanting to kill American service personnel overseas.
Abousamra was questioned by Border Patrol agents as he fled the country in 2006, but he was not detained for what Deslauriers calls "operational reasons."