An armed suspect is holding at least four people hostage at a synagogue near Fort Worth, Texas Saturday.

The Fort Worth Star-Telegram reports that the FBI and Texas Department of Public Safety were negotiating with the suspect, who entered the Colleyville, Texas’ Congregation Beth Israel during Saturday morning services. At least four people — including Rabbi Charlie Cytron-Walker — were believed to be among the hostages. 

The suspect also threatened that he had bombs in the area. Soon after taking the hostages, the suspect was heard negotiating with authorities via a Facebook livestream for the synagogue’s service. On the livestream — which was being viewed by 8,000 people before it was abruptly turned off — the male suspect could be heard ranting about religion and demanding the release of his sister.

According to ABC News, the suspect is believed to be demanding the release of convicted terrorist Aafia Siddiqui, the woman known as “Lady al Qaeda” who was sentenced to 86 years in prison for the assault and attempted murder of a U.S. soldier during a 2010 interrogation; Siddiqui, who allegedly had ties to al-Qaida, is behind bars at Carswell Air Force Base near Fort Worth.

In 2014, following reports that ISIS demanded the release of Siddiqui in exchange for a 26-year-old American woman who was kidnapped in Syria, Siddiqui’s family said in a statement, “While we deeply appreciate the sincere feelings of those who, like us, wish to see the freedom of our beloved Aafia, we cannot agree with a ‘by any means necessary’ approach to Aafia’s freedom. Nor can we accept that someone else’s daughter or sister suffer like Aafia is suffering.” (ISIS had previously demanded Siddiqui’s release in exchange for murdered American journalist James Foley.)

“Negotiators have contact with this person and are working to come to a safe resolution,” Colleyville Police Sgt. Dara Nelson told reporters, adding that there was “no threat to the general public.”

“I am closely monitoring the unfolding hostage situation at Congregation Beth Israel in Colleyville,” Fort Worth Rep. Marc Veasey tweeted. “I know the Rabbi and his wife Adena very well. I’m praying for his safety and his congregants, and hope that this situation is resolved soon.”

Congregation Beth Israel synagogue, established in 1999, was the first Jewish congregation in Northeast Tarrant County, CNN reports.

The Anti-Defamation League tweeted Saturday, “ADL is aware of the ongoing situation in Colleyville, TX and is engaged with local and federal authorities and the community’s leaders.”