A Milwaukee beer company’s corporate office turned into a bloody nightmare Wednesday when a disgruntled worker fired earlier in the day returned with a gun to kill five workers before shooting himself.

Police were called to the sprawling Molson Coors Beverage Co. complex on West Highland Avenue just after 2 p.m. local time to find the worst mass shooting in Wisconsin’s history, as employees learned via email eight minutes later there was an active shooter lurking in their stairwell, the Milwaukee Journal Sentinel reported.

Terrified employees huddled in closets and behind locked doors, frantically texting family members and loved ones, multiple reports said.

The unidentified shooter was an employee, the company said in a statement.

He’d been fired earlier in the day but returned to the campus with a stolen name tag and a silenced gun, WBBM-TV reported.

The Journal Sentinel said he had two handguns — only one with a silencer.

He then struck the plant’s brewery, one of Milwaukee’s most popular tourist destinations, and slaughtered five people before turning the gun on himself.

All five victims were employees, Chief Alfonso Morales said during an evening press conference, noting the shooter was 51 and a Milwaukee resident. No other injuries were reported.

“There was a horrific shooting that has occurred,” Milwaukee Mayor Tom Barrett told reporters at the scene earlier Wednesday.

“It is a horrible, horrible day for the employees here. It’s a very rough day for anyone who is close to this situation.”

The state’s governor, Tony Evers, tweeted about the tragedy, saying “Our hearts go out to the families of those whose lives were senselessly taken.”

Alderman Russell Stamper, whose district falls within the facility, decried the shooting as another callous disregard for human life.

“The vile and heinous deadly violence that was perpetrated at the brewery complex today has no place in our society and makes no sense,” Stamper wrote in a statement.

“The cold disregard for human lives and the lack of value for human life that was shown must be categorically denounced across Milwaukee, across Wisconsin and throughout our nation.”

Recordings from the city’s emergency radio system painted a horrific picture of what first responders were witnessing when they got to the scene.

“Start building rescue task forces,” one fire commander was heard barking over the radio, according to the Journal Sentinel.

The Milwaukee police deemed the threat no longer active by 4:37 p.m. local time and announced there was a family staging area for employees at the Harley Davidson parking lot on Juneau Avenue.

The MolsonCoors tweeted it was working “closely” with the Milwaukee Police Department.

“Our top priority is our employees and we’ll provide updates in conjunction with the police as we are able,” the company wrote on Twitter.

The office will remain closed for the week and the brewery is shut for the “time being,” the company said.

President Donald Trump addressed the shooting during an unrelated press conference late Wednesday, calling the gunman a “wicked murderer.”

“Our hearts break for [the victims] and their loved ones. It’s a terrible thing,” Trump said.

At least 600 people work at the facility, commonly known in the area as “Miller Valley.”

With Post wires