A Molson Coors Beverage Co employee has shot five co-workers to death before taking his own life at the company’s beer-brewing complex in Milwaukee, the latest episode in a rising tide of gun violence already reverberating in the US race.

Authorities offered few details of the circumstances surrounding Wednesday afternoon’s shooting and no explanation for what might have triggered the carnage.

“This is a tragic day for our city, this is a tragic day for our state,” mayor Tom Barrett said outside the landmark facility known to locals as the old Miller brewery.

Some 1,400 employees work at the Molson Coors campus, which consists of about 20 buildings, and most were forced to remain holed up inside for several hours as police methodically swept the facilities to secure the property.