Hostage incident at Texas synagogue a terrorist act and hate crime: FBI

The FBI said on Friday that it's treating the recent hostage situation at a Texas synagogue as a terrorist act and hate crime.

An international federal investigation is ongoing after a rabbi and three members of his Dallas-Fort Worth-area congregation were taken hostage Saturday by an allegedly armed man who authorities said was demanding the release of a convicted terrorist.

The incident "underscores the continued threat violent extremists pose to religious institutions, particularly Jewish institutions and other Jewish targets," Matthew DeSarno, the special agent in charge of the FBI's Dallas field office, said during a press briefing.

"The FBI is and has been treating Saturday's events as an act of terrorism targeting the Jewish community," DeSarno continued. "It was committed by a terrorist exposing an antisemitic worldview."

The suspect "repeatedly demanded the United States release a convicted al-Qaida terrorist in exchange for the safe return of the hostages," which met the definition of terrorism under federal law, said DeSarno, adding that forcibly holding hostage the victims as they exercised their right to worship was a federal hate crime.

"We recognize that the Jewish community in particular has suffered violence and faces very real threats from across the hate spectrum, from domestic violent extremists to foreign terrorist organizations. And because of that, the FBI considers the enduring threats to the community to be among our very highest priorities," DeSarno said.

The suspect, who died in the incident when an FBI hostage rescue team breached the synagogue, was identified by authorities as Malik Faisal Akram, 44, a British citizen.

Rabbi Charlie Cytron-Walker was leading Shabbat services at the Congregation Beth Israel in Colleyville on Saturday morning when, according to law enforcement officials, Akram interrupted the service and allegedly claimed he'd planted bombs in the synagogue.

Authorities believe the location was intentionally targeted because it was the closest synagogue to Carswell Air Force Base near Fort Worth, where the convicted terrorist is being held.

DeSarno did not identify the prisoner by name, though multiple law enforcement sources told ABC News the armed suspect was demanding the release of Aafia Siddiqui, who was convicted of assault and attempted murder of a U.S. soldier in 2010 and sentenced to 86 years in prison.

DeSarno said the suspect was aware that foreign terrorist organizations previously had tried to negotiate the release of the prisoner by exchanging American hostages. DeSarno said he doesn't know of any personal connection between the suspect and the convicted terrorist.

In the days since the incident, law enforcement officials have received a "high volume of leads" and have interviewed all those they believe Akram had interacted with since arriving in the U.S. on Dec. 29, according to DeSarno, who did not elaborate if any were considered accomplices. Authorities have not detained anyone locally in connection with the incident.

Investigators have been digging into the suspect's social media and personal devices to try and find out more about his travel and associates, as well as determine how he allegedly acquired a firearm, DeSarno said. No explosives were recovered at the scene.

The FBI is also working with international partners, including the U.K., as part of the investigation. Two men were arrested in England on Thursday morning as part of the investigation, British authorities said.

The 10-hour standoff ended with all four hostages safely escaping as the situation had gone from "bad to significantly worse," said DeSarno.

"The professionalism and expertise in the negotiation team combined with the composure and judgment of the hostages set the conditions for a successful resolution," he said.

Cytron-Walker said he had the cellphone number of Colleyville Police Department Chief Michael Miller and was able to text and communicate with him about the hostage situation as it unfolded.

"We were constantly looking for an opportunity to leave, and it was very, very hard to find an opportunity where we all could leave," Cytron-Walker told reporters Friday.

Hostage negotiators successfully negotiated the release of one of the hostages. As three remained, Cytron-Walker said he threw a chair at the hostage-taker so they could make their escape.

"I stand up here before you with great gratitude just to be alive," Cytron-Walker said. "With gratitude to God, with gratitude for all of those individual human efforts that allow us to be here today, I'm just overflowing with gratitude."

Cytron-Walker invited all those interested to pray with the congregation Friday night and Saturday morning through its Facebook Live program as the community tries to find a "sense of peace" after the harrowing incident.

"We all desperately, desperately need that sense of peace," he said. "And I would extend that not only to the Jewish community but extend that to all communities."

ABC News' Matthew Fuhrman contributed to this report.