Eight people have been shot dead by a gunman at a FedEx facility in the US city of Indianapolis before the shooter killed himself, police said.
Several other people were injured in the incident near Indianapolis International Airport, and four were taken to hospital, police spokesperson Genae Cook said.
One person is said to be critically ill.
The gunman was not immediately identified, and investigators are in the process of conducting interviews and gathering information.
Ms Cook said it is too early to tell whether the shooter was an employee at the facility.
Police were called to reports of gunfire just after 11pm on Thursday, and officers observed an active shooting scene, Ms Cook said. The gunman later killed himself.
FedEx earlier said it was cooperating with authorities and working to get more information, adding: “We are aware of the tragic shooting at our FedEx Ground facility near the Indianapolis airport.
“Safety is our top priority, and our thoughts are with all those who are affected.”
Family members gathered at a local hotel to await word on loved ones.
Some said employees are not allowed to have their phones with them while working shifts at the facility, making it difficult to contact them, WTHR-TV reported.
Live video from news outlets at the scene showed crime scene tape in the car park outside the facility.
A witness who said he works at the facility told WISH-TV that he saw a man with a gun after hearing several gunshots.
Jeremiah Miller said: “I saw a man with a submachine gun of some sort, an automatic rifle, and he was firing in the open.”
Another man told WTTV that his niece was sitting in her car in the driver’s seat when gunfire erupted.
“She got shot on her left arm,” said Parminder Singh.
“She’s fine, she’s in the hospital now.”
He added that his niece did not know the shooter.
The shooting was the latest in a string of mass shootings across the US in recent months.
Eight people were fatally shot at massage businesses in Atlanta, and 10 died at a supermarket in Boulder, Colorado, last month.
This was at least the third mass shooting this year in Indianapolis.
Five people, including a pregnant woman, were shot and killed in January, and a man was accused of killing three adults and a child before abducting his daughter during an argument at a home in March.