Five Dead, Several Injured In Mass Shooting In Newsroom

"There is nothing more terrifying that hearing multiple people get shot while you're under your desk and then hear the gunman reload."

Five people are dead and several are seriously injured after a mass shooting in Maryland, United States, police have confirmed.

A suspect is in custody. Police are yet to identify him but have confirmed that he's an adult white male.

A single shooter entered the building housing the Capital Gazette in Annapolis. Phil Davis, a journalist at the Gazette, tweeted that the gunman "shot through the glass door to the office and opened fire on multiple employees."

He later added: "There is nothing more terrifying that hearing multiple people get shot while you're under your desk and then hear the gunman reload."

Authorities were on the scene within 60 seconds.

The weapon has yet to be confirmed but police say that it is a long gun, a category of firearm with a long barrel.

Authorities also recovered an item suspected of being an explosive device, which has now been "taken care of".

CBS News is reporting that the suspect is refusing to identify himself, and damaged is own fingertips in an effort to avoid identification.

Police were on the scene in 60 seconds, and did not exchange gunfire with the suspect.

170 people were evacuated from the building with their hands up, and directed to a reunification centre at a local shopping centre.

SWAT teams and quick responders have secured the building, with investigators now taking over to determine why, how and when the incident happened.

Witnesses are being interviewed by police before being reunited with their families.

Editor of the Gazette, Jimmy DeButts, has tweeted that he's "devastated and heartbroken", throwing his support behind the local paper.

"There are no 40 hours weeks, no big paydays - just a passion for telling stories from our community," he tweeted.

"We are there in times of tragedy. We do our best to share the stories of people, those who make our community better. Please understand, we do all this to serve our community.

Earlier during the day, an at the paper, Anthony Messenger, had tweeted earlier: "Active shooter 888 Bestgate please help us."

Maryland Governor Larry Hogan said that he was "absolutely devastated to learn of this tragedy", asking the public to heed all warnings and stay away from the area.

"Praying for those at the scene and for our community," he said.

President Donald Trump said his "thoughts and prayers are with the victims and their families."

This story is developing.