A pro-ISIS media group issued an online threat against an FBI special agent-in-charge over the arrest of one of their American members on a charge of providing material support and resources to a foreign terrorist organization.

Ashraf Al Safoo, 34, of Chicago made his first court appearance on Friday and is scheduled to appear for a detention hearing on Thursday. At the time of his arrest he worked as a web developer for BlueBolt Solutions, a Chicago software company; his LinkedIn profile said he specializes in Microsoft technologies.

Al Safoo is a member of Khattab Media Foundation, which disseminates propaganda and recruitment materials on behalf of ISIS including posters, videos and articles released on sites including YouTube, Twitter and Facebook.

In response to his arrest, Khattab just released a new poster depicting a jihadist about to behead a victim face-down on a street with a city skyline in the backdrop. “From Khattab Foundation to Jeffrey The Dog of Romans,” states the message. “We read your message YOU son of an infidel mother and the answer will be what YOU will see not what YOU will hear.”

They added the hashtags #OUR_FLAMES and #USA.

The special agent in charge of the FBI’s Chicago Division is Jeffrey S. Sallet; he was quoted in the Justice Department’s press release announcing Al Safoo’s arrest.

“The safety of the American public is the FBI’s highest priority,” said Sallet, who began his role leading the Chicago office last November. “Homegrown terrorists and ‘lone-actor’ operators continue to represent a threat to the homeland. The arrest today should send a clear message to these individuals: No matter who you are or where you may be, we will find you and arrest you.”

“This case would not be possible without the combined efforts of the Chicago Joint Terrorism Task Force, and in particular the work of our partners at the Chicago Police Department and the Department of Homeland Security,” Sallet added.

The head crudely photoshopped on the orange-jumpsuited victim in the Khattab poster resembles Sallet.

According to the affidavit, Al Safoo worked with Khattab Media Foundation in its core invitation-only Staff Group, which had about 21 members as of this April, and its Writers Group, which had about 13 members.

Last December, Al Safoo allegedly rallied operatives to work harder on the ISIS social media effort. “You’re not dedicating more time for Twitter..! What’s going on?! Accounts are available, praise Allah, so what are you waiting for?! Don’t let the weakness afflict you. Get rid of your laziness, and…, o dear. And how can they defeat us while we’re so many, praise Allah?! Be careful with the accounts and increase it, and spoil the lives of the infidels,” he posted in the Staff Group.

At one point Khattab considered a merger with another ISIS propaganda group, but Al Safoo told members that a decision not to proceed was made “in accordance with the State’s [ISIS’] instructions.”

In May, Al Safoo explained the group’s workflow to a new member. “Every article written by an author comes to me first then I forward it to the reviewers then it is forwarded to the designers then to classification/management/control then to upload and publishing,” he wrote.

The group posts material calling for lone jihadist attacks and encourages would-be terrorists to seize attack opportunities, including a push for Christmas terrorism.

Al Safoo faces up to 20 years behind bars on the conspiracy charge.