Molson Coors shooter identified as campus electrician, 51, seeking revenge after feud with co-worker, reports say

Anthony Ferrill was an "active employee" at brewery though police have not revealed a motive in killing that left five others dead

Police respond to a shooting at Molson Coors brewery in Milwaukee that left six dead, including the shooter. (AP)

The gunman suspected of fatally shooting five coworkers at Molson Coors before killing himself has been identified as 51-year-old electrician Anthony Ferrill, whose alleged feud with another employee had reportedly boiled over before he returned to the facility and opened fire, according to reports.

Molson Coors Beverage Company, the multinational brewing company whose brands include the Miller and Coors beer lines, employs 1,200 people at its Milwaukee facility.

Milwaukee Police Chief Alfonso Morales confirmed that Mr Ferrill was "an active employee" at the facility, though police did not report a motive.

The victims included machinists and other electricians at the brewery.

Victims include Jesus Valle Jr, 33; Gennady Levshetz, 51; Trevor Wetselaar, 33; Dana Walk, 57; and Dale Hudson, 50.

According to court records, Mr Ferrill sued the company's health benefits program in 2015 following a history of back pain.

He reportedly told a coworker that he believed he was being discriminated against because he was African-American, and he often argued with another electrician at the facility.

At brief press conference on Thursday, Milwaukee Mayor Tom Barrett said "it's difficult to put into words how all of us feel right now", though he did not speculate about the shooter's motive.

Mr Ferrill allegedly left the building and returned with two guns on Wednesday.

Police received reports about a shooting at the campus around 2pm as employees received texts and emails warning an active shooter was in one of the buildings.

"There are no words to express the deep sadness many of us are feeling right now", Molson Coors CEO Gavin Hattersley said in a statement following the shooting.

The brewery has shut down for the remainder of the week to allow the families and employees to mourn.