Three people were killed and 14 others were wounded when a gunman opened fire at a packed bar in downtown Austin early Sunday — and the FBI’s Joint Terrorism Task Force is investigating the attack.

Police responded to reports of a male shooting at Buford’s Backyard Beer Garden — near the University of Texas-Austin — just before 2 a.m., officials said at a press conference.

Three officers who were patrolling the entertainment district responded to the scene in 57 seconds, confronted the gunman and “returned fire,” killing the unidentified suspect.

The gunman reportedly stormed the bar with a handgun and an assault rifle, according to the Austin-American Statesman.

The FBI’s Joint Terrorism Task Force has joined the investigation into the mass shooting — indicating that the motive of the attack could be related to terrorism.

“Officers immediately transitioned, came over East 6th to West 6th Street and were faced with the individual with a gun,” Austin Police Chief Lisa Davis said.

Three victims died at the scene.

First responders, who arrived to assist in less than a minute, rushed 14 other patients to nearby hospitals.

Three victims are listed in critical condition, officials said.

No one has been identified so far.

Just hours before the shooting, the popular bar shared videos on its Instagram story showing the bar jam-packed young revelers drinking and dancing to a DJ.

The clips show the unsuspecting crowd belting out Miley Cyrus’ “Party in the USA” and Kelly Clarkson’s “Since You Been Gone” as they’re blasted by a smoke machine.

The bar, which is open between 12 p.m. and 2 a.m. on the weekends, was gearing up to close for the night when gunfire erupted.

Officials said they will release more information as it becomes available throughout the day.

“Our hearts go out to the people that are victims of this and I want to reiterate my thanks to our public safety officers and officials that so rapidly were on the scene, they definitely saved lives,” Austin Mayor Kirk Watson said.

Moments before the shooting, revelers were enjoying live music on a packed dance floor, according to video posted to the beer garden’s social media.

Officials noted federal agents were helping with the investigation into the shooting and would share further details throughout the day.

Buford’s, a large night-life bar, can hold up to 700 people and features a stage, basketball, skeeball and video games.

Buford’s Backyard Beer Garden did not immediately respond to The Post’s request for comment.

A motive behind the shooting was not revealed.

The conditions of the other 11 wounded victims were not announced

“This is a situation that we are going to be talking about probably all day,” Davis added.

The Austin Police Department told community members searching for loved ones who were at the shooting to contact the APD’s Victim Services Unit at 512-974-5037.