Six people are dead after a Molson Coors Beverage Co. employee killed five of his co-workers and then fatally shot himself during a rampage at the company's Milwaukee campus Wednesday, authorities said.

The suspected gunman is a 51-year-old man who worked at the company, Milwaukee Police Chief Alfonso Morales told reporters during a news briefing. Morales did not identify any of the victims, pending family notifications.

"It's a terrible day for Milwaukeeans," Morales said.

Mayor Tom Barrett called the shooting a "tragic day for our city, a tragic day for our state."

"Six families actually are grieving and will be grieving because of the horrific act of this individual," he said. "Because 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."

Molson Coors CEO Gavin Hattersley was at a company conference in Houston when he was made aware of the shooting. He was en route to Milwaukee, authorities said.

In a statement, he said: "There are no words to express the deep sadness many of us are feeling right now."

"The most important thing is that we support and care for each other," he said.

Milwaukee police responded to a "critical incident" at the campus after reports of a shooting just before 2:10 p.m., authorities said. The incident was treated as an active shooter situation.

The company tweeted about the "active situation" just before 2:30 p.m. and said: "There is an active situation at our Milwaukee facility and we are 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."

Employees were alerted to the chaos through company text messages and emails.

The Milwaukee Police Department tweeted that a "critical incident" occurred near the 4000 block of W. State Street and asked for everyone to stay away from the area.

The company told the Milwaukee Journal Sentinel in an email that the shooter was located in or near Building 4 in the second-floor stairwell.

Molson Coors and the Milwaukee police did not respond to Fox News' requests for comment.

A company employee told WTMJ-TV that they were told to shelter in place. Officers from the Milwaukee County Sheriff's Office, Marquette University Police Department, the U.S. Marshals and other federal agencies also responded to the scene.

A local elementary school was placed on lockdown as a precaution, the station reported.

Molson Coors Beverage Co. operates had more than 1,000 employees working at the Milwaukee campus at the time of the shooting. The 160-year-old brewery is an iconic attraction in a city known for its brewing industry.

James Boyles told the Milwaukee Journal Sentinel that his wife, Lasonya Ragdales, works at Molson Coors in the claims department. She was texting from inside the building and told her husband that there was an active shooter and she was locked in a room with a bunch of co-workers.

The company is locally known as "Miller Valley," a sprawling complex that features the brewery, along with packaging and distribution centers. The facility is also home to corporate customer service, finance, human resources and engineering offices.

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President Trump extended "my deepest condolences" to the victims during a White House briefing on his response to the coronavirus. He said a "wicked murderer" opened fire and killed several people.

"A number of people were wounded, some badly wounded," Trump told reporters. "Our hearts break for them and their loved ones. It's a terrible thing."

House Speaker Nancy Pelosi, D-Calif., tweeted her condolences to the victims and called on Congress to "take action" to end gun violence.

"We are closely following developments surrounding the shooting in Milwaukee, Wisconsin," Pelosi wrote. "Our prayers are with the families who have lost loved ones and the first responders protecting the community. Congress has a duty to them all to take real action to #EndGunViolence."

Wisconsin U.S. Sens. Ron Johnson and Tammy Baldwin also shared their thoughts via social media.

"Gun violence has taken too many lives in Milwaukee and the mass shooting today is heartbreaking," Baldwin, a Democrat, tweeted. "I want to thank the first responders who ran into harm's way and saved lives. My office is standing by to help the #MKE community in the wake of this tragedy."

Johnson, a Republican, offered prayers to those impacted by Wednesday's violence.

Molson's corporate offices will remain closed through the rest of the week and the brewery will be closed for an extended period, Hattersley said.

The attack was the 11th mass shooting in the city since 2004, Lt. Gov. Mandela Barnes said.

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"We shouldn't accept this," he said. "This is not the way things should be. We should never grow comfortable in the face of these repeated tragedies all across America and especially here at home."

Molson acquired MillerCoors in 2016 and retired the beer brand.

The Associated Press contributed to this report.