TRAVIS AIR FORCE BASE, Calif. (CBSNewYork/AP) — Travis Air Force Base, northeast of San Francisco, was temporarily locked down Wednesday due to what the base called a “real world security incident.”

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The base issued a security alert shortly after 3:30 p.m. Wednesday asking people to shelter in place and to lock doors and windows.

Marie Lowe, a civilian who answered the phone at the base’s public affairs office, said details were sketchy and officials were investigating because they didn’t know exactly what is going on.

CBS Sacramento’s Steve Large posted video from outside the base, where announcements calling for a lockdown can be heard from inside the base.

Base officials asked on Facebook for the public to stay away to ensure emergency responders can do their work.

Just after 5 p.m. local time, the base said emergency personnel originally responded to reports of gunshots which were ultimately determined to be a false alarm.

Wednesday’s lockdown came on the same day that the base had been conducting security lockdown exercises, but officials say the incident was not part of the drill.

The false alarm came on a day marked by violence.

In Virginia, a gunman wounded Rep. Steve Scalise and several others during practice for a baseball game featuring congressional Republicans.

James T. Hodgkinson, 66, was fatally shot by police who had been guarding Scalise, the House majority whip.

In San Francisco, a UPS employee opened fire inside a package delivery facility, killing three co-workers and himself, authorities said.

(© Copyright 2017 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)

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