Police are evacuating Civic Center Plaza and UN Plaza after reports of a possible gunman in the area. 

"Area around Civic Center is blocked off—reports of yellow tape from Market to Golden Gate," says journalist Julia Chan on Twitter. 

According to ABC7, both pedestrians and motorists have been cleared from the plaza. It's not clear if anyone has been injured. The suspect has been described as an adult male, holding something that may possibly be a weapon.

A man with an apparent gun in #civiccenter . He's pacing back and forth by the trees. 😳😳 pic.twitter.com/VIxWCeSWxB

— Stefffffff (@steffwong) September 24, 2016

SFPD talking to this man, believed to be armed in Civic Center Plaza. Standoff continues...Area has been evacuated.. #abc7now pic.twitter.com/7sQOMiz4IV

— Cbarnard (@CornellBarnard) September 24, 2016

Police standoff with poss. armed suspect happening in SF Civic Center Plaza. Pedestrians, motorists being evacuated from area.#abc7now pic.twitter.com/hoxU6ftJHR

— Cbarnard (@CornellBarnard) September 24, 2016

#BREAKING Poss. armed man in SF Civic Center. SFPD evacuating people from City Hall to UN Plaza. #abc7now pic.twitter.com/2QLGvsjyms

— Cbarnard (@CornellBarnard) September 24, 2016

Update, 1:07pm: According to ABC7, a SWAT team has just arrived at Civic Center.

SFPD has evacuated all of Civic Center plaza @ city hall. Standoff w/ man, possibly armed continues.#abc7now pic.twitter.com/0cDTjEJv8b

— Cbarnard (@CornellBarnard) September 24, 2016

Update, 1:43pm: The standoff is still ongoing. KPIX has reported that the suspect is being described as "agitated and rambling," and is known to have threatened "suicide by cop" in the past.

UPDATE: #SF police surround #UNPlaza and talk to a suspect who is possibly armed with a gun. https://t.co/dZtLO39DGr pic.twitter.com/dxTXyoLwqf

— ABC7 News (@abc7newsbayarea) September 24, 2016

Civic Center remains shut down:

The whole civic center area is closed. I can't go home. 😱 pic.twitter.com/m6UXVFDkYD

— Naz Erkan 🙋🏼 (@naz_erkan) September 24, 2016

Update, 2:42pm: Police confirmed to NBC Bay Area that the man is armed with a semi-automatic handgun, but has yet to fire it. They also said that he may be suicidal, as was initially rumored. They do not believe the incident is terror-related.

Update, 4:16pm: The standoff remains ongoing. Police have told NBC Bay Area that the suspect is a white San Francisco resident in his 40s, and that he has threatened to use the gun on himself. It's unclear whether he is on any drugs, but they are aiming to get him to surrender peacefully. 

The man discussed wanting "to end his life" and "take out other people," Ofc. Carlos Manfredi told NBC. A SWAT team and crisis negotiators remain on the scene.

Update, 6:16pm: After nearly six hours, the man has surrendered, and the shelter in place order is being lifted. 

Code 4. Suspect surrendered peacefully without further incident. Good work Crisis Negotiators & everyone out at the scene. pic.twitter.com/n7UvLeXfj0

— Officer Manfredi (@OfficerManfredi) September 25, 2016

The shelter in place for #SanFrancisco #CivicCenter area has been lifted. Please continue to avoid the area due to traffic congestion. #SF

— San Francisco DEM (@SF_emergency) September 25, 2016