On Tuesday, The FBI asked the public for help identifying individuals who have traveled (or are planning on traveling) overseas to fight with terrorist groups, such as ISIS (also known as ISIL).

“We need the public’s assistance in identifying U.S. persons going to fight overseas with terrorist groups or who are returning home from fighting overseas,” said Michael Steinbach, assistant director of the FBI’s Counterterrorism Division, in a statement.

The statement included a short video clip of an English-speaking individual seen in a propaganda video released in September by ISIS. The man in the video is wearing desert camouflage, a shoulder holster and is able to switch flawlessly between English and Arabic. In the longer version of the video, the man can be seen standing in front of prisoners as they prepare their own graves.

“We’re hoping that someone might recognize this individual and provide us with key pieces of information,” Steinbach said. “No piece of information is too small.”

According to a bureau official cited by Bloomberg News, the FBI has gotten a “substantial number of tips” from the public following the release of the video clip.

The FBI believes that the individual in the video has a North American accent and is one of approximately a dozen Americans fighting in Syria for ISIS, according to FBI Director James Comey.

Although ISIS is certainly in the spotlight as they battle to take over the besieged town of Kobani, a Kurdish enclave in Syria, the FBI notes that there have been past cases of U.S. citizens traveling or planing to travel overseas to fight with terrorist groups. In 2010, for example, a Chicago man planned to travel to Somalia to join al Shabaab. In 2012, a New York man tried to travel to Yemen to support al Qaeda. Most recently, a Chicago teen was taken into custody for allegedly trying to journey overseas to join ISIL.

“These homegrown violent extremists are troubled souls who are seeking meaning in some misguided way,” Comey said during a Sunday interview on 60 Minutes. “And so they come across the propaganda and they become radicalized on their own independent study, and they’re also able to equip themselves with training again on the Internet, and then engage in jihad after emerging from their basement.”