The names of the victims or gunmen were not released immediately.
“The (gunman) got into the parking lot, and I think he got out of his vehicle and started firing quickly …” Indianapolis Deputy Police Chief Craig McCartt reported on CNN on Friday.
Police arrived “at a very chaotic scene, with casualties and witnesses running everywhere,” McCartt said.
McCartt said he believes the gunman committed suicide when officers found him. No police officer fired him, he said.
The motive for the shooting was not immediately known, Indianapolis police spokeswoman Genae Cook said.
At least four survivors were taken to a hospital with gunshot wounds, as well as someone with a wound believed to be caused by shrapnel, McCartt said.
One person was in critical condition, police said.
On Friday, police were trying to make sense of the crime scene as relatives of FedEx employees gathered at a nearby hotel to wait for news about their loved ones.
“I thought they would shoot me”
At first, Jeremiah Miller and Timothy Boillat thought the sound was from a car, but after hearing more, Miller stood up and saw a man with a gun, he said.
“After hearing the shots, I saw a body on the ground behind a vehicle,” Boillat said. The two men walked out of the building and watched as about 30 police cars responded.
“Thank God I was here because I thought they would shoot me,” Miller told the station.
Police are asking anyone who was at the scene and may have left for safety or medical treatment to contact them to provide information about the shooting.
FedEx said in a statement that it is aware of the “tragic shooting” at the Indianapolis facility.
“Safety is our top priority and our thoughts are on everyone affected. We are working to gather more information and cooperate with investigating authorities,” company spokesman Jim Masilak said in an email to CNN .
“I am communicating with local authorities to get all the details of the attack and my office is ready to help all those affected in the way we can.”
CNN’s Joe Sutton and Keith Allen contributed to this report.