Ramos filed a defamation claim in 2012 against the paper but the case was dismissed, CNN reports. Another Capital Gazette employee later confirmed Messenger was safe.
"The shooter is in custody and is being interrogated at this time", city spokesman Steve Schuh said.
"Our thoughts and prayers are with all that are affected", Walters said.
However, Anne Arundel County police said during a Thursday evening news conference that they could not confirm that information.
The building is secure, according to officials. "That has been taken care of". The shooter's name or a possible motive for the shooting was not yet clear. The newspaper is one of several tenants in the building.
The suspect shot through a glass door.
The suspect is "a white male, adult male, and the gun that was used is described as a long gun", meaning a rifle or a shotgun, Lieutenant Ryan Frashure told journalists.
The number of injuries was estimated at three people, Frashure said.
A senior federal law enforcement source says the suspect was also carrying fake grenades.
Another update was expected at 8 p.m. CBS News reported that the shooter inflicted damage to his fingertips in an effort to not be identified by prints.
Tom Marquardt, the newspaper's editor and publisher until 2012, said he and other Gazette employees anxious about how to stop Ramos' harassment.