The incident came a week after President Joe Biden branded USA gun violence an "epidemic" and an "international embarrassment" as he waded into the tense debate over gun control, a powerful political issue in the United States.
This is the worst Sikh massacre in the U.S. after the Oak Creek Gurdwara mass shooting in Wisconsin on August 5, 2012, where seven members of the community were killed.
"I also urged Congress to hear the call of the American people - including the vast majority of gun owners - to enact commonsense gun violence prevention legislation, like universal background checks and a ban of weapons of war and high-capacity magazines", Biden said.
The FBI is assisting local police in their investigation into the motive behind the attack and officials said they are hopeful security video from the building will be able to assist them in that investigation.
The Thursday night slayings came a week after President Joe Biden branded USA gun violence an "epidemic" and an "international embarrassment" as he waded into the tense debate over firearms control, a sensitive American political issue.More news: Latest updates: Philip's coffin in Inner Hall ahead of funeral
Cook said that the gunman had died and the public is not believed to be in immediate danger.
Some said employees were not allowed to have their phones with them while working shifts at the facility, making it hard to contact them.
The recent surge in United States mass shootings began on March 16 when a gunman shot eight people to death, including six Asian woman, at three Atlanta-area day spas before he was arrested. "It stains our character and pierces the very soul of our nation", he said in a statement.
The tragic killings have once again brought gun violence and targeted hate crimes at the centre of security discussions in the states.
"I saw a man with a submachine gun of some sort, an automatic rifle, and he was firing in the open", Jeremiah Miller said. "I thought he saw me and so I immediately ducked for cover", he added.
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"Out of eight, four are Sikh community members", Gurinder Singh Khalsa said. Her daughter, Jessica, works in the facility and she had not heard from her.
FedEx Chairman and Chief Executive Officer Frederick Smith called the shooting a "senseless act of violence".
Eight people were killed.
The Indianapolis deputy chief of criminal investigations, Craig McCartt, told CNN the shooting "probably only lasted one to two minutes", after it began in the parking lot.
That came less than a week after a man shot and killed eight people, including six women of Asian descent, at spas in Atlanta, Georgia.
Indianapolis Mayor Joe Hogsett said the community must guard against resignation and "the assumption that this is simply how it must be and we might as well get used to it".More news: U.S. prepares sanctions against Russian Federation over cyber attacks, election interference