A gunman killed at least eight people and injured several others in a shooting rampage at a FedEx facility in Indianapolis before turning the gun on himself, officials said early Friday.

The unidentified attacker opened fire about 11 p.m. at the company’s operations center near the Indianapolis International Airport. It is unknown if the shooter was a FedEx employee or what his motive was.

Police spokeswoman Genae Cook said authorities responded to a report that shots had been fired and “arrived to an active shooter incident.”

“Preliminary information is that the alleged shooter has taken his own life here at the scene,” she said, adding that there was no longer any threat to the public.

Four people were transported to hospitals, one in critical condition with gunshot injuries, and three others with various other injuries, she said.

Two more were treated at the facility by medical personnel and released, while “multiple” others had walked to hospitals nearby, Cook added.

The identities of the dead victims have not been released pending notification of the next of kin.

“It is very heartbreaking and, you know, in the Indianapolis Metro Police Department, the officers responded, they came in, they went in and they did their job,” Cook said. “And a lot of them are trying to face this because this is a sight that no one should ever have to see.”

Craig McCartt, deputy chief of criminal investigations for the Indianapolis police, told CNN early Friday that the shooting “probably lasted one to two minutes.”

“It was very short,” McCartt said, adding that the shooter exited his vehicle and immediately began shooting in the parking lot before entering the facility and continuing his attack.

He said he believed the gunman encountered police officers inside and took his own life.

McCartt added that a FedEx policy that prohibits employees from carrying cellphones while working had complicated the reunification effort.

One man who was working at the plant, which reportedly employs more than 4,000 people, told WISH-TV that he saw the gunman unleash a hail of gunfire.

“I saw a man with a submachine gun of some sort, an automatic rifle, and he was firing in the open. I immediately ducked down and got scared,” Jeremiah Miller told the station.

“My friend’s mother, she came in and told us to get inside the car. What we’ve been doing [since] is telling everyone, our co-workers not to go to work today,” he said.

“Thank God for being here because I thought I was going to get shot,” Miller added.

Timothy Boillat, another employee, told WISH-TV that he saw dozens of police cars arriving as the shooting unfolded.

“After hearing the shootings, I did see a body on the floor,” Boillat said. “Luckily, I was far enough away to where he [the shooter] didn’t see me.”

Police established a family unification center at the Holiday Inn on Stansted Drive, the Indianapolis Star reported.

Indianapolis police will work with the state police to investigate the shooting and interview people at the scene and at local hospitals.

“This is going to be an investigation that goes on throughout the day,” Cook said.

Parminder Singh, the uncle of one of the victims, told Fox 59 that his niece was in her car when the gunman started shooting.

“She called as I was asleep at home. She said there was a shooting in the FedEx. So we just drove from Brownsburg,” Singh told the news outlet.

Another man said his wife, who works at the facility, texted him to tell him there was an active shooter.

“We communicated back and forth for a while, she’s since notified me she’s OK,” Ian Johnston told Fox 59. “After I communicated with her for a while, then it went silent for a while, so I came here just to see what was going on and she texted me, ‘I’m OK.’”

In a statement, FedEx said: “We are deeply shocked and saddened by the loss of our team members following the tragic shooting at our FedEx Ground facility in Indianapolis.

“Our most heartfelt sympathies are with all those affected by this senseless act of violence. The safety of our team members is our top priority, and we are fully cooperating with investigating authorities,” it added.

Congressman André Carson (D-Ind.), whose district includes 80 percent of Indianapolis, said on Twitter that he was “heartbroken by the mass shooting at the FedEx facility here in Indianapolis and praying for all affected by this tragedy. I am communicating with local authorities to get all details of the attack and my office stands ready to help everyone affected any way we can.”

The incident in Indianapolis follows a spate of recent mass shootings across the US.

At the end of last month, four people, including a child, were gunned down in an office building in Orange, California.

On March 22, 10 people were killed in a shooting at a grocery store in Boulder, Colorado.

That came less than a week after a man killed eight people, including six women of Asian descent, at spas around Atlanta.

Thursday’s shooting was the third in Indianapolis this year. In January, five people including a pregnant woman were killed. Three adults and a child were killed in March.

With Post wires