On the FBI website, you'll find a recording of accused terrorist Ahmad Abousamra. Investigators hope someone will hear his voice, recognize him and turn him in.

"It's often easy for individuals to change their appearance through clothes, makeup, facial hair -- it's not often easy for them to disguise their voice," said Special Agent in charge of the investigation Richard DeLauriers.

Though they won't comment on the timing, Wednesday, the FBI launched a social media campaign and put up a reward of $50,000 for information leading to the arrest of Abousamra.

The 31-year-old computer programmer and UMass Boston graduate was indicted a few years ago on nine terrorism-related charges, including trying to train to kill US service members overseas and conspiring to provide material support to Al-Qaida.

"Detecting, preventing and deterring a terrorist attack here inside the United States is the FBI's top investigative priority," said DeLauriers in a conference room in the FBI's Boston office.

Abousamra has dual citizenship in the US and Syria; investigators think he fled to Syria with his wife and young daughter in 2006 after being questioned by the FBI about trips he took to Pakistan and Yemen.

The FBI says he was inspired by the 9/11 attacks and grew close with Tarek Mehanna, the Sudbury, Mass. man convicted on terrorism charges earlier this year. According to FBI documents the men were actively trying to "radicalize others," but the FBI says no other arrests are imminent.

Abousamra used to live in this 3-family home in Mansfield. The couple who says they bought if from him several years ago did not want to answer our questions.

A woman who identified herself as the homeowner said, "Why are you asking all these questions, please?" before asking us to turn off our cameras.

When we asked her husband how he knew Abousamra and what he thinks of the FBI manhunt he said, "It is uncomfortable. I don't want to talk about it please."

Longtime neighbors who say the family was quiet call the accusations against Abousamra disturbing.

"To know that our boys go overseas and fight for our country and we have people right here in our country that -- you know it's just -- you know. With the way things are in this country, I'm not surprised," said Rich Mcauly.

"I didn't think we'd have it gone, but I thought we'd have it cut down since 9/11 and to have a terrorist that lived next to you -- it is a little frightening," Jeff Widrow added.

FBI agents say using social media has gotten results in other investigations and they are optimistic in this case.

If you have any information, you can call the tipline at 1-800-CALL-FBI or log on to fbi.gov. You can listen to voice clippings of Abousamra here.