Another employee of the Gazette, Bill Wagner, tweeted that he's "okay" and was not in the newsroom at the time of the shooting.
Police gave no immediate details on the gunman or the motive for the attack at The Capital Gazette and said the suspect was being interrogated.
A reporter at The Capital, the name of the newspaper, tweeted that a single individual shot multiple people.
Capital Gazette Communications publishes multiple newspapers, including the Capital and the Maryland Gazette. One hundred seventy people were safely evacuated from the building, which houses several businesses in addition to the newspaper.
Officials say the suspect is a white male who is believed to have used a shotgun.
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Acting Anne Arundel County Police Chief William Krampf confirmed the fatalities and injuries at a news conference shortly after 4:30 p.m. It started at around 2:35 p.m., according to WTTG-TV in Washington D.C.
Maryland Governor Larry Hogan said he was "absolutely devastated to learn of this tragedy in Annapolis", adding he was in contact with authorities and Maryland State Police who were on the scene assisting county police.
Lt. Ryan Frashure, another spokesman for Anne Arundel County police, said on WJLA that officers are "doing everything to get people out safe".
The Bureau of Alcohol, Tobacco, Firearms and Explosives said it is responding to reports of the shooting. "Please, heed all warnings and stay away from the area". Police were dispatched to the Sun newsroom in Baltimore after the shooting, but the Sun reports that the police presence there was just a precaution.
Five people have been reported killed after a gunman opened fire at The Capital newspaper in Annapolis, Maryland. He said he was "praying for those at the scene and for our community".
This story is developing.