Police have found an explosive device at a newspaper targeted by a gunman who shot dead five people.
Five people have been confirmed dead in the shooting in the US state of Maryland, and at least three people have been "gravely injured" as investigators question the suspect.
"There's five fatalities that we know of. There's several other persons that are gravely injured," deputy police chief of Anne Arundel county Bill Krampf told reporters.
Earlier, an explosive device was been found at the site.
"We did recover what we thought was an explosive device. It has been taken care of. We don't anticipate having any more explosive devices," deputy police chief Krampf said.
A law enforcement official said the crime is not being treated as a terrorist incident.
The Federal Bureau of Investigation is on the scene assisting local authorities, the official said.
The Capital newspaper is located in a four-storey office building in Annapolis, the capital of the US state of Maryland. It is owned by the Capital Gazette Communications company.
Reporter heard the 'gunman reload'
Reporters in the Capital newsroom at the time described the terrifying experience.
Crime reporter Phil Davis tweeted that a "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," Davis said.
Anthony Messenger, a Gazette intern, according to his Twitter account, tweeted: “Active shooter at 888 Bestgate please help us." He also wrote that an editor was shot.
One law enforcement source told CBS News the suspect is a male in his twenties, who had no identification on him. Two law enforcement sources told CBS News the suspect used a shotgun.
Anne Arundel County Executive Steve Schuh said he was heartbroken over the news of multiple deaths.
"Those fatalities are so sad," he said. "And I don't know what to say other than our thoughts and prayers are with them and their families."
Explosive found at site
Deputy police chief Krampf said the site has now been "tactically secured" and will remain closed to the public while criminal investigators scour the site.
"The building has been tactically secured. What that means is our SWAT team and our quick responders have been through the building," he said. "There are no more persons in the building that are a threat to anyone."
"Our criminal investigation division is now on the scene. We have released the scene to our criminal investigators so they can start the process of what occurred, how it occurred and why it occurred."
Meanwhile, law enforcement officials in Baltimore and New York have deployed police officers to major media outlets as a precaution, authorities said.
"We're deploying units from our Critical Response Command to news outlets throughout New York City," said Officer Andrew Lava, an NYPD spokesman.
"There is no active threat at this time," he said.
President Trump briefed
President Donald Trump's press secretary on Thursday described the shooting as an attack on "innocent journalists."
"Strongly condemn the evil act of senseless violence in Annapolis, MD," Sarah Sanders tweeted.
"A violent attack on innocent journalists doing their job is an attack on every American. Our prayers are with the victims and their friends and families."
The President posted a message of support on Twitter.
"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," he wrote.
Maryland Governor Larry Hogan said he is grief-stricken.
"It's a tragic situation," he told reporters. "We thank the people that came in and kept it from being worse. The response time was incredible."
'Unite to end violence'
Several lawmakers said the incident should speed efforts to end gun violence.
"My heart is with the families, friends and loved ones of the victims as we learn more about this terrible situation," Chris Van Hollen, the state's junior senator said. "We must unite to end the violence."
A recent study found that Americans own 40 percent of the world's firearms despite accounting for only four percent of the global population.
Of the 857 million guns owned by civilians, 393 million are in the United States - more than all of the firearms held by ordinary citizens in the other top 25 countries combined, according to the Small Arms Survey.
Advocates of tougher gun laws have stepped up their efforts in the wake of numerous school shootings this year, including the killing of 17 people at a Parkland, Florida high school in February and the killing of 10 people at a Texas high school in May.
So far the results have been relatively modest. Florida has raised the legal age to buy firearms from 18 to 21, while Texas Governor Greg Abbott focused on mental health and improving school safety in his list of recommendations following the Santa Fe shooting in the rural southeast of his state.
But he also called for requiring gun owners to report lost firearms and for allowing law enforcement to temporarily take away guns from people determined by courts to be "potentially dangerous" to themselves or others.
- with agencies.