A man faces a federal charge for allegedly selling the gun used in the Texas synagogue hostage situation earlier this month, authorities said.
Henry Williams, 32, faces one charge of being a felon in possession of a firearm in connection with the hostage crisis at Congregation Beth Israel in the Fort Worth suburb of Colleyville on Jan. 15.
The armed suspect, identified by authorities as 44-year-old British citizen Malik Faisal Akram, died in the incident when an FBI hostage rescue team breached the synagogue after an 11-hour standoff.
Investigators allege Williams sold Akram a Taurus G2C pistol on Jan. 13, two days before the hostage incident.
The FBI said it discovered Williams' alleged ties to Akram through an analysis of Akram's phone records after his death.
Agents first interviewed Williams on Jan. 16, during which he allegedly said he recalled meeting "a man with a British accent," the Department of Justice said.
Agents interviewed Williams again after his arrest on an outstanding state warrant on Monday, during which he allegedly confirmed he sold Akram the handgun at an intersection in South Dallas after viewing a photo of the suspect, according to the Justice Department.
"Williams allegedly admitted to officers that Mr. Akram told him the gun was going to be used for 'intimidation' to get money from someone with an outstanding debt," the Department of Justice said in a statement.
Cellphone records for both men also show their phones were in close proximity on Jan. 13, according to prosecutors.
Williams was arrested Tuesday on the firearm charge and made his first appearance before a magistrate judge Wednesday afternoon. According to the Department of Justice, Williams was previously convicted of aggravated assault with a deadly weapon and attempted possession of a controlled substance.
"Federal firearm laws are designed to keep guns from falling into dangerous hands. As a convicted felon, Mr. Williams was prohibited from carrying, acquiring, or selling firearms," U.S. Attorney for the Northern District of Texas Chad Meacham said in a statement. "Whether or not he knew of his buyer's nefarious intent is largely irrelevant -- felons cannot have guns, period, and the Justice Department is committed to prosecuting those who do."
A detention hearing has been scheduled for Monday. ABC News has reached out to Williams' attorney for comment.
A rabbi and three members of the synagogue were taken hostage during the incident. All four managed to escape unharmed.
FBI agents said the suspect was demanding the release of a convicted terrorist and believe the location was intentionally targeted because it was the closest synagogue to Carswell Air Force Base near Fort Worth, where the prisoner is being held.
Multiple law enforcement sources told ABC News the 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.
In the weeks since 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.
Four men have also been arrested in England within the past week as part of the probe, British authorities said.