The gunman, who also shot himself dead, is believed to be a 51-year-old employee of the Molson Coors owned brewery, based in Milwaukee, Wisconsin.
The victims were all workers at the site.
In a statement, Gavin Hattersley, CEO of Molson Coors Beverage Company, urged people to keep the family of his 'fallen teammates' in their thoughts.
Mr Hattersley said,' The police have since confirmed the shooter, who was an active brewery employee, is now deceased.'
He added, 'Unfortunately, I am devastated to share that we lost five other members of our family in this tragic incident. The police are still working to notify their relatives, so I am unable to provide more information at this time.'
Emergency services were called to the site around 2pm on Tuesday local time.
The facility was placed on lockdown, with staff forced to hide under their desks, while the gunman was on the loose.
Nearby businesses were also locked down.
lwaukee Mayor, Tom Barrett, said it was a 'tragic day.'
'There were individuals who went to work today just like everybody goes to work, and they thought they were going to go to work, finish their day and return to their families. They didn't and tragically they never will,' he said.
The incident is believed to be the 54th mass shooting in the US this year, with a mass shooting defined as having four or more victims.