A lone gunman walked into the Capital Gazette in Annapolis on Thursday with a shotgun and killed at least five people, police said.

The mayhem happened around 2:30 p.m. inside the paper’s newsroom, in an office park outside the city center.

Anne Arundel County police officials confirmed that five people were killed and several others “gravely injured.” A suspect was apprehended after the shooting. He reportedly used a shotgun to take out his victims.

Phil Davis, a Gazette reporter, tweeted about the harrowing ordeal.

“A single shooter shot multiple people at my office, some of whom are dead,” he said. “Gunman shot through the glass door to the office and opened fire on multiple 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 said.

Speaking to The Baltimore Sun, Davis said the inside of the newsroom was “like a war zone.”

“I’m a police reporter. I write about this stuff — not necessarily to this extent, but shootings and death — all the time,” he said. “But as much as I’m going to try to articulate how traumatizing it is to be hiding under your desk, you don’t know until you’re there and you feel helpless.”

Davis said the gunman shot multiple people before he randomly stopped firing.

“I don’t know why. I don’t know why he stopped,” he told the Sun.

Police officials said they “engaged” the suspect upon their arrival and arrested him at the scene without incident. Law enforcement sources told The Post that he is a white male, between 30 and 40 years old. They said that he’s not been cooperating with police.

The man had no identification on him when he was taken into custody and the FBI has been unable to find any information on him in the system, the sources said.

It took cops a mere 60 seconds to respond to the shooting and find the suspect. Anne Arundel County Executive Steve Schuh told CNN that a suspicious package was discovered at the scene, containing what was believed to be flammable liquids. Nothing appeared to be ignited.

Former Gazette editor Tom Marquardt told ABC News the paper’s offices are easily accessible to the public.

“The newsroom is very open,” he said. “We wanted people to feel free to come in and discuss the issues of the day. We dealt with threats in the past. We were always very concerned about security. It was an open building. We didn’t want to been seen like a closed institution.”

Marquardt claimed there were “angry readers” and constant threats due to some of the paper’s election endorsements.

“I personally got threats,” he said. “Others got threats. In my day we did call the police a couple times. But these were mostly anonymous. Nothing like this.”

Meanwhile, NYPD brass on Thursday mobilized cops to major news outlets across the city in a precautionary response to the shooting.

President Trump and other politicians took to Twitter on Thursday evening to commend authorities on the fast response and offer their condolences in the wake of the tragedy.

“Prior to departing Wisconsin, I was briefed on the shooting at Capital Gazette in Annapolis, Maryland,” Trump tweeted. “My thoughts and prayers are with the victims and their families Thank you to all of the First Responders who are currently on the scene.”

Additional reporting by Larry Celona