Several people were also wounded, including five who were taken to the hospital. As officers arrived, they came upon an active shooter, she said. Two other people were treated at the scene by medical personnel and were released.
Christina Valor said she had learned about the shooting from the news and driven to the hotel because her sister, Natalie Valor, worked there and had not been in touch.
"This made me stand up and actually look out the entrance door, and I saw a man with a submachine gun of some sort, an automatic rifle, and he was firing in the open", Miller told the station.
"Somebody went behind their vehicle to the trunk and then got another gun", he said, adding: "Then I saw one body on the floor". "What I ended up doing was ducking down to make sure he did not see me because I thought he would see me and he would shoot me".
The FedEx facility reportedly has at least 4,000 employees.More news: Gunman kills eight before taking own life at Indianapolis FedEx site
"We're still trying to ascertain the exact reason and cause for this incident", Cook said.
The Indianapolis police department's deputy chief, Craig McCartt, told CNN that police did not fire any shots in the incident.
This event is the latest in a recent string of mass shootings across the U.S. It was the country's deadliest shooting since 10 people were killed March 22 at a grocery in Colorado.
It was at least the third mass shooting this year in Indianapolis alone.
"Last night and into the morning in Indianapolis, yet again families had to wait to hear word about the fate of their loved ones", Biden said.
The families' agonizing waiting was exacerbated by the fact that most employees aren't allowed to carry cellphones inside the FedEx building, making contact with them hard. Mindy Carson said early Friday, fighting back tears. She said her daughter was OK and she was going to meet her, but didn't say where. The gunman later killed himself.More news: India reports record 200,000 new covid-19 cases as outbreak spreads
Indianapolis Mayor Joe Hogsett lamented that the city was "confronted with the horrific news of yet another mass shooting, an act of violence that senselessly claimed the lives of eight of our neighbors".
FedEx said in a statement early Friday that it was cooperating with authorities and working to get more information.
Mass shooting at Indianapolis FedEx facility leaves eight dead. Let us look out for one another, as we have done all throughout this past challenging year, and as we send our most heartfelt sympathies to all who have been affected by this bad act of violence.
A man told WTTV that his niece was sitting in the driver's seat of her vehicle when the gunfire erupted, and she was wounded. "She's fine, she's in the hospital now", Parminder Singh said.
"And you know, Indianapolis Metro Police Department, the officers responded", Cook said.More news: Biden tells Putin to ease tensions on Ukrainian border, proposes summit