DALLAS — A shooter opened fire at an outlet mall in the Dallas suburb of Allen on Saturday, sparking scenes of panic, and emergency officials confirmed fatalities in the latest mass shooting in the United States.

At least nine wounded people were rushed to area hospitals, emergency officials said.

Some of the victims were as young as five years old, CNN reported.

An off-duty police officer was in the mall on an unrelated call when gunfire broke out around 3:30pm (2030 GMT), said chief Brian Harvey of the Allen, Texas, police department.

"He heard gunshots, went to the gunshots, engaged the suspect and neutralized the suspect," Harvey said. "He also then called for ambulances."

Harvey confirmed there had been fatalities but declined to give a death toll, saying "we do not have an accurate count."

Allen Fire Chief Jonathan Boyd said his department "transported nine victims to area trauma facilities."

Texas Governor Greg Abbott called the mass shooting an "unspeakable tragedy."

President Joe Biden "has been briefed on the shooting," a White House official told reporters.

Authorities initially thought there might be a second shooter at Allen Premium Outlets, a sprawling shopping complex in the city of Allen, 40 kilometers north of Dallas, CNN said.

Police combed through stores in the mall, and photos and drone video from the scene showed frantic shoppers and store employees rushing into parking lots.

Harvey later said police believe the unidentified shooter, who CNN said was wearing tactical gear, "acted alone."

Janet St. James, a spokesperson for Medical City Healthcare, which operates multiple trauma facilities in North Texas, said it received eight patients from the shooting, ranging in age from five to 61, NBC News reported.

A father who arrived at the mall after his daughter, who was inside, phoned to tell him about the shooting, also told CNN that police had informed him there may have been a second shooter.

"We saw the police outside the door, and they told us we had to go, and that they are still looking for the person," Jaynal Pervez said, according to CNN.

"There's no more safe places. I don't know what to do."

Pervez later told broadcaster CBS that scenes in the mall parking lot were chaotic.

"I saw the shoes around there, people's cell phones on the street," he said.

With more firearms than inhabitants, the United States has the highest rate of gun deaths of any developed country -- 49,000 in 2021, up from 45,000 the year before.

There have been more than 195 mass shootings -- defined as four or more people wounded or killed -- so far this year in the United States, according to the Gun Violence Archive. — AFP