The FBI's Joint Terrorism Task Force has joined the investigation after at least two people were killed and 14 others wounded in a mass shooting overnight at a popular bar in Austin, Texas, authorities said Sunday. The gunman was also killed, police said.

There was no initial word on the shooter's identity or motive.

Austin Police Chief Lisa Davis said police received a call for reports of a man shooting at Buford's, a beer garden in the city's entertainment district.

Fourteen people were hospitalized, and three were in critical condition, Austin-Travis County EMS Chief Robert Luckritz said.

"We received a call at 1:39 a.m., and within 57 seconds, the first paramedics and officers were on scene actively treating the patients," Luckritz said.

At a briefing on Sunday, the FBI said the Joint Terrorism Task Force is engaged in the investigation. They said there were indicators on the subject and in his vehicle that suggest a potential nexus to terrorism, but that it is too early to determine the motivation.

They said a pistol and a rifle were found at the scene.

Two law enforcement sources tell CBS News that investigators believe the shooter has a history of mental health issues. They are looking at whether the shooter was influenced by extremist ideology, specifically Islamic extremism, but they say the mental health issues appeared to be significant.

Sen. Ted Cruz, a Texas Republican, told "Face the Nation with Margaret Brennan" on Sunday morning that "we don't know for sure" if the shooting was related to terrorism.

"At this point, we don't know what the evidence will show in terms of whether this was an act of terrorism," Cruz said.

Davis noted how fortunate it was that there was a heavy police presence in Austin's entertainment district at the time, enabling officers to respond quickly as bars were closing.

"Officers immediately transitioned ... and were faced with the individual with a gun," she said. "Three of our officers returned fire, killing the suspect."

She called the shooting" a tragic, tragic incident."

Austin Mayor Kirk Watson said his heart goes out to the victims, and he praised the swift response of first responders.

"They definitely saved lives," he said. (CBS News)

Update news