Authorities said on Friday that it was still too early to know what motivated a gunman who killed eight employees at a FedEx facility in Indianapolis and wounded several others before taking his own life.
The incident - the latest in a spate of mass shootings in the United States - unfolded at a FedEx (FDX.N) operations center near Indianapolis International Airport in Indiana after 11 pm local time on Thursday night, police said.
It lasted only a couple of minutes and was already over by the time police responded to the scene, Craig McCartt, the Indianapolis police department's deputy chief, told a news briefing on Friday.
Witnesses described a chaotic attack, as the gunman opened fire in the parking lot before entering the facility and continuing to shoot, leaving victims both inside and outside the building. Officers found the suspect dead of an apparent self-inflicted gunshot wound.
FBI Indianapolis Special Agent in Charge Paul Keenan said it would be "premature to speculate" on the gunman's motive. Authorities have not yet publicly named the suspect or any victims, though Keenan said investigators were searching the suspect's home.
NBC's New York affiliate reported on Twitter that the gunman was 19-year-old Brandon Scott Hole, citing three law enforcement sources.
The massacre is the most recent in a series of US mass shootings that has again pushed the issue of gun violence to the political foreground.
Indianapolis - the capital of the Midwestern state of Indiana - alone has seen two mass shootings this year. In January, police say a teenager shot and killed four family members and a pregnant woman.
US President Joe Biden, in a statement, said he had ordered flags lowered and reiterated his call for Congress to pass gun restrictions.
"Too many Americans are dying every single day from gun violence," he said. "It stains our character and pierces the very soul of our nation. We can, and must, do more to act and to save lives."
Earlier this month, Biden announced limited measures to tackle gun violence that included a crackdown on self-assembled "ghost guns." But more stringent measures face an uphill battle in a divided Congress, where Republican lawmakers have long opposed any new gun limits.
Nearly 20,000 Americans died last year as a result of gun violence, not including suicide - 25 percent higher than in 2019, and more than in any other year in at least two decades, according to figures compiled by the Centers for Disease Control and Prevention.
Eight people were shot to death at three day spas in the Atlanta area in mid-March, raising fears that the gunman had targeted Asian Americans amid a rise in hate crimes. Days later, a gunman killed 10 people at a Colorado grocery store.
There have been 147 mass shootings in 2021, defined as incidents in which at least four people were shot, according to the Gun Violence Archive, a non-profit website that tracks firearm-related incidents.
Friday also marked the 14th anniversary of the deadliest school shooting in US history at Virginia Tech, which saw 32 people killed.
"Last night, Indianapolis was revisited by the scourge of gun violence that has killed far too many in our community and our country," Mayor Joe Hogsett said at the briefing.
A FedEx employee, Levi Miller, told NBC's Today Show he saw a "hooded figure" holding what appeared to be an AR-style semi-automatic rifle who shouted and opened fire outside the facility.
"I thought he saw me, and so I immediately ducked for cover," he said.
Another worker at the air freight facility told local television station WRTV that he was eating when he heard what sounded like "two loud metal clangs" followed by more shots.
"Somebody went behind their car to the trunk and then got another gun," he said. "Then I saw one body on the floor."
Five people were taken to hospitals with gunshot wounds, including one in critical condition, police said. Two more were treated at the facility itself by medical staff and released.
Hours after the shooting, employees' family members, friends and colleagues gathered at a 'family unification center' that authorities set up at a nearby hotel. Some relatives expressed frustration that they were unable to reach workers at the site, where many employees are barred from having their mobile phones by a company policy intended to avoid distractions.
In a message to staff, FedEx Chief Executive Officer Frederick Smith said that the eight victims were all employees.
"First and foremost, I want to express my deepest sympathies to the families, friends, and co-workers of those team members," said Smith, who added that the company is cooperating with investigators.