Eight people were killed in a mass shooting at an Indianapolis FedEx facility on Thursday night, Indianapolis Metropolitan Police Department spokeswoman Genae Cook said.

Authorities were aware of multiple other injured victims in hospitals, one of whom was in critical condition, she said during a media briefing early Friday.

Police believe the shooter took his own life and there is "no active threat to the community at this time," Cook said.

It is unclear what motivated the shooting, but investigations are ongoing and will continue into most of the day Friday, she said.

Police arrived at the scene of the shooting at around 11:00 p.m. local time to an active-shooter situation and entered the facility without hesitation, Cook said.

"The officers responded, they came in, they went in and they did their job," Cook said. A lot of them are trying to face this because this is a sight no one should ever have to see."

' I thought I was going to get shot'

Two employees inside the building at the time told CNN affiliate WISH-TV that they heard as many as ten gunshots.

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 weapon, he said.

"After hearing the shootings I did see a body on the floor behind a vehicle," said Boillat. The two men left the building and watched as about 30 police cars responded, Boillat said.

"Thank God for being here because I thought I was going to get shot," Miller told the station.

Police are asking anyone who was at the scene and may have left for safety or for medical treatment to contact 262-TIPS or the Indianapolis Metropolitan Police homicide officer to provide information on the shooting.

In a statement, FedEx said it was aware of the "tragic shooting" at the Indianapolis facility.

"Safety is our top priority, and our thoughts are with all those who are affected. We are working to gather more information and are cooperating with investigating authorities," company spokesperson Jim Masilak said in an email to CNN.

Indiana Congressman Andre Carson who represents the 7th District of Indiana, including Indianapolis, tweeted that he was heartbroken by the mass shooting.

"I am communicating with local authorities to get all details of the attack and my office stands ready to help everyone affected any way we can."