Authorities said they found an Iranian flag and photos of regime leaders in the apartment of the gunman in the shooting outside a bar in Austin, Texas, on Sunday morning.

The flag and the images were discovered during a search of the suspect's home, according to CBS News, after the shooting early Sunday morning that left three people dead and 14 wounded.

The shooter was also wearing a sweatshirt that read "Property of Allah" and an undershirt featuring an Iranian flag when he carried out the attack, according to law enforcement sources.

The suspect, identified as Ndiaga Diagne, was a 53-year-old naturalized U.S. citizen who was born in Senegal and lived in Pflugerville, Texas, multiple federal law enforcement sources told Fox News.

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Diagne first entered the U.S. in 2000 on a B-2 tourist visa before becoming a lawful permanent resident six years later after marrying a U.S. citizen. He became a naturalized U.S. citizen in 2013.

His criminal history includes being arrested in Texas in 2022 for collision with vehicle damage.

The shooting happened outside Buford’s Backyard Beer Garden shortly before 2 a.m. along Sixth Street, a nightlife destination filled with bars and music clubs located near the University of Texas at Austin.

Police Chief Lisa Davis said the gunman "put his flashers on, rolled down his window and began using a pistol shooting out of his car windows, striking patrons of the bar that were on the patio and that were in front of the Bar." The suspect then drove westbound on Sixth Street to Wood Street, parked, exited the vehicle with a rifle and continued shooting at pedestrians, but he never entered the bar.

Police shot and killed the gunman, who used a pistol and a rifle in the shooting.

"Today is a difficult day for our city and the University," the university's president, Jim Davis, said on X. "We are deeply saddened by the tragedy that occurred early this morning in downtown Austin. Our prayers are with the victims and all those impacted, including members of our Longhorn family. We are also grateful to the first responders who acted quickly to save lives, and to our UT counselors and staff members who have provided care and support throughout the day."

The FBI said the shooting was a possible act of terrorism, as authorities continue to investigate.

"Obviously, it's still way too early in the process to determine an exact motivation, but there were indicators on the subject and in his vehicle that indicate potential nexus to terrorism," Alex Dorn, acting special agent in charge of the FBI’s San Antonio Field Office, said at a Sunday press conference.

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"Again, it's still too early to make a determination on that. That's why we are investigating it very closely with our partners with Austin police department," Dorn added.

Asked by a reporter if the case involved domestic or international terrorism, Dorn said the Joint Terrorism Task Force is engaged.

"We're just at this point prepared to say that it was potentially an act of terrorism," he said.

The U.S. has been cleared to use British bases for limited strikes on Iran’s missile capabilities after Prime Minister Keir Starmer signed off on the plan, and while U.K. Defense Secretary John Healey stated on Sunday Britain had "stepped up alongside the Americans."

"The only way to stop the threat is to destroy the missiles at source, in their storage depots or the launchers which are used to fire the missiles," Starmer confirmed in a recorded statement to the nation.

"The U.S. has requested permission to use British bases for that specific and limited defensive purpose," he said. "We have taken the decision to accept this request."

The decision came amid escalation across the Middle East in the wake of U.S. and Israeli strikes on Iran and Tehran’s retaliatory missile and drone attacks, raising fears of a broader regional conflict.

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On Feb. 28, in the wake of Operation Epic Fury, Starmer confirmed British planes "are in the sky today" across the Middle East "as part of coordinated regional defensive operations to protect our people, our interests and our allies."

Healey went on to disclose Sunday that two Iranian missiles were fired in the direction of Cyprus, where Britain maintains key sovereign base areas.

The Royal Air Force confirmed that Typhoon jets operating from Qatar as part of the joint U.K.-Qatar Typhoon Squadron successfully intercepted an Iranian drone heading toward Qatar.

About 300 British personnel are stationed at a naval facility in Bahrain, where Iranian missiles and drones struck nearby areas.

"We’re taking down the drones that are menacing either our bases, our people or our allies," Healey told "Sunday Morning with Trevor Phillips" on Sky. "We’ve stepped up alongside the Americans. We’ve stepped up our defensive forces in the Middle East. We’re flying those sorties."

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Healey also made sure to stress that the U.K. had "no part" in the U.S. and Israeli strikes on Iran and insisted all British actions were defensive. "All our actions are about defending U.K. interests and defending U.K. allies," he said.

When asked if the U.K. would join the U.S. in offensive action, Healey said, "I'm not going to speculate," according to Sky News.

Downing Street also confirmed Feb. 28 that Starmer and President Donald Trump had spoken by phone about the "situation in the Middle East," the BBC reported.

Fox News Digital has reached out to Downing Street for comment.