(CNN) — As investigators seek to learn more about the man killed after holding hostages at a synagogue over the weekend, the FBI on Monday is investigating the Colleyville, Texas, attack as “terrorism-related,” the agency said.

Expressing its relief the hostages were not physically hurt and touting its focus on extremist threats to the Jewish community, the FBI noted hostage taker Malik Faisal Akram “spoke repeatedly about a convicted terrorist who is serving an 86-year prison sentence in the United States,” its statement said.

“This is a terrorism-related matter, in which the Jewish community was targeted, and is being investigated by the Joint Terrorism Task Force,” the statement said, declining to provide more details due to the continuing investigation.

The convicted terrorist the FBI mentions is believed to be Aafia Siddiqui, who is serving a federal prison sentence in Fort Worth after being found guilty of attempted murder and other charges in an assault on US officers in Afghanistan. She was not involved in the Colleyville attack, her attorney said Saturday.

Akram, a 44-year-old British national, was armed when he entered the Congregation Beth Israel on Saturday morning as the house of worship livestreamed its Sabbath service on Facebook and Zoom, Colleyville Police Chief Michael Miller said. The livestream captured a portion of the 11-hour standoff before ending.

Akram took four people, including the synagogue’s rabbi, hostage. One man was released unharmed around 5 p.m., Colleyville police said. The rest of the victims were rescued that evening as an FBI rescue team killed Akram, the agency said.

Two teenagers were arrested in south Manchester, England, in connection with the Texas incident and were awaiting questioning, UK Counter Terrorism Police for Greater Manchester said Sunday.

Attacks on Jewish people are on the rise, the Anti-Defamation League warns. While the majority of the anti-Semitic incidents involve harassment and vandalism, there have also been violent assaults, and on at least six occasions since 2016, the attacks have turned deadly.

Hostage taker arrived in the US weeks ago

Akram arrived at New York’s John F. Kennedy International Airport about five weeks ago, a US law enforcement source familiar with the investigation told CNN. Authorities are investigating how he traveled from New York to Texas.

Akram arrived legally, a separate federal law enforcement source said, and was vetted before his arrival, meaning his information would’ve been cross-checked with classified and unclassified information available at the time. He was on no US government watch list, the source said.

British intelligence told its US counterparts that a preliminary review of its databases show no worrying information on Akram, the source said, but UK authorities are continuing to review their systems.

Between January 6 and 13, Akram spent three nights at Union Gospel Mission Dallas, a homeless shelter, according to shelter CEO Bruce Butler. “We were a way station for him,” he said. “He had a plan. He was very quiet. He was in and out.”

Akram left the mission for the last time Thursday morning, two days before the hostage situation, according to their records. Butler did “not recall seeing him, but he was not there long enough to build any relationships. We had a lot of new faces coming in because of the cold weather,” he said.

Based on discussions with Akram as well as audio from the livestream, officials believe Akram was motivated by a desire to see the release of Siddiqui, who is serving an 86-year sentence in Fort Worth’s Federal Medical Center, Carswell after being found guilty of seven charges, including attempted murder and armed assault, in a 2008 attack on US officers in Afghanistan.

Siddiqui “has absolutely no involvement with” the taking of hostages in Texas, her attorney said.

Akram’s brother says the family is “absolutely devastated” by his actions and they “apologize wholeheartedly to all the victims,” he wrote in a statement on Facebook, adding the family was in contact with police during the incident.

Rabbi credits training courses

Rabbi Charlie Cytron-Walker, who was among the hostages, credited “multiple security courses” with providing congregants the proper training to survive.

“In the last hour of our hostage crisis, the gunman became increasingly belligerent and threatening,” Cytron-Walker said. “Without the instruction we received, we would not have been prepared to act and flee when the situation presented itself.”

A member of the congregation watched the livestream for more than an hour, listening to Akram yelling in different languages, she said. The suspect vacillated between being apologetic and “screaming hysterically,” talking repeatedly about how he hated Jewish people, she said.

“At any moment, I thought there was going to be a gunshot,” the member said, adding Akram claimed to have a bomb.

As the standoff came to a close, a nearby CNN team heard a bang followed by a short blast of rapid gunfire coming from the synagogue’s direction.

Crime scene investigators recovered a firearm they believe belonged to Akram, the Bureau of Alcohol, Tobacco, Firearms and Explosives said.

A community comes together

During and after the ordeal, the local Jewish community and those of other faiths issued expressions of support for the synagogue. Congregant Anna Salton Eisen was moved by how neighbors — and state and national leaders, including Gov. Greg Abbott and President Joe Biden — conveyed their sympathies, she said.

“The response from our neighbors, communities, from law enforcement, from churches, from mosques, was so overwhelming and intense and immediate that I really feel like if we have to face a crisis, that people will have our back,” she said.

Asked how the congregation will respond, she said, “For all of us, the first thing is regaining some sense of safety.” She was already feeling safer, she said, because of the resolve shown by those around them.

“We are welcome and a part of this community,” she said. “Even though anti-Semitism may be increasing and may be present, so is the remedy, so is the unity and the strength and the resolve to overcome these issues.”

Cytron-Walker actively works to bring together members of the Christian, Jewish and Islamic faiths in the metro area, leaders from the Islamic Center of Southlake said.

The rabbi brought sweets to their Eid festival and attends festivities during the Islamic holy month of Ramadan, former center president Shahzad Mahmud said. Cytron-Walker and his wife have been friends of the Islamic center since “Day One,” Mahmud said.

“We want to make sure that the Jewish community knows that we stand with them as they always stand with us when we feel like we are in trouble by criminals,” Mahmud said.

In a Sunday Facebook post, Cytron-Walker said, “I am thankful and filled with appreciation for all of the vigils and prayers and love and support, all of the law enforcement and first responders who cared for us, all of the security training that helped save us.

“I am grateful for my family. I am grateful for the CBI Community, the Jewish Community, the Human Community. I am grateful that we made it out. I am grateful to be alive,” he wrote.

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