WATCH LIVE: Authorities to give update on deadly newsroom shooting at 10:15

(WJZ via CNN)

ANNAPOLIS, Md. – Five people were killed, several more injured and one person was taken into custody Thursday after a gunman went on a rampage at the Capital Gazette newspaper in Annapolis, Maryland, authorities said.

William Krampf, acting chief of police for Anne Arundel County, said beside those killed in the shooting, several people are "gravely injured." The identity of the suspect was not immediately released.

The Baltimore Sun, which owns the Annapolis newspaper, says a reporter told them of the shooting. Reporter Phil Davis described what unfolded in a series of vivid tweets.

Click image above to see live aerials from scene

"A single shooter shot multiple people at my office, some of whom are dead," Davis tweeted, explaining that the gunman shot through the glass door and then opened fire on employees.

"There is nothing more terrifying than hearing multiple people get shot while you're under your desk and then hear the gunman reload," he wrote in a subsequent tweet.

Intern Anthony Messenger pleaded for help in a jarring tweet posted shortly before 2:45 p.m. "Active shooter 888 Bestgate please help us," the tweet said.

Anne Arundel County Police and the Bureau of Alcohol, Tobacco, Firearms and Explosives confirmed they were investigating the shooting, saying they had resources on scene clearing the premises.

On TV reports, people could be seen leaving the building with their hands up, as police officers urged them to depart through a parking lot and officers converged on the building.

Arminta Plater, spokesperson for Anne Arundel Medical Center, said two patients had arrived there but she did not know their conditions. She could not immediately provide additional details.

President Donald Trump tweeted his condolences, saying his "thoughts and prayers are with the victims and their families."