Federal, local law enforcement prepare for possible armed protest at California state Capitol

Authorities are bracing for potential violence at California's state Capitol building amid warnings from the FBI of the possibility of attacks at all 50 state capitals and at the U.S. Capitol in the days leading up to the Jan. 20 inauguration of President-elect Joe Biden.

Investigators believe some of the people who plan to gather for demonstrations are members of extremist groups that are calling for "storming" state, local, and federal government courthouses and administrative buildings in the event Donald Trump is removed as president prior to Inauguration Day.

"The FBI received information about an identified armed group intending to travel to Washington, DC, on 16 January," reads an internal FBI bulletin obtained by ABC News. "They have warned that if Congress attempts to remove POTUS via the 25th Amendment a huge uprising will occur."

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The group is also planning to "storm" government offices in every state on Jan. 20, regardless of whether the states certified electoral votes for Biden or Trump.

The Sacramento Bee reports FBI field offices across the country have been alerted to the possible violence and command posts have set up to communicate with state and local law enforcement, including the California Highway Patrol, which has jurisdiction over the state Capitol.

Gov. Gavin Newsom says California's Capitol has a heightened level of security, but he has not made a decision on whether to activate the National Guard in anticipation of the armed protests.

"We have a big challenge ahead of us next week, with what happened last week and what some people are calling for with the inauguration -- not just in D.C., but all over our country," said Sacramento police Chief Daniel Hahn. "It is very much a potential here and we are doing everything that we can to ensure that that doesn't happen."

The FBI bulletin included a map that showed the extent of law enforcement activity related to potential threats surrounding election certification and the inauguration.

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Ed Farrell, the former Deputy U.S. Marshal in Chicago, said regular law enforcement will need National Guard backup at some locations.

"There's obviously a big effort to stop and deter these actors before they become operational, which is going to be big," Farrell said. "They're going to be gathering intelligence on these individuals, they will be surveilling these individuals. And if they're able to get probably cause to arrest them, I would imagine you're going to see some arrests of bad actors. Additionally, I think you're going to see an elevated security presence at all government facilities, they're going to limit access to the buildings, they're going to put up barricades, they're going to close doors. Things to prevent people from coming in during this elevated risk time."

Army Gen. Daniel Hokanson, chief of the National Guard Bureau, told reporters Monday that the Guard is also looking at any issues across the country,

"We're keeping a look across the entire country to make sure that we're monitoring, and that our Guards in every state are in close coordination with their local law enforcement agencies to provide any support requested."

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The FBI has received nearly 45,000 digital media tips that are now being reviewed.

The rampage through the halls of Congress sent lawmakers of both parties and Trump's own vice president into hiding, as crowds called for Mike Pence's lynching for his role overseeing the vote count. The scene also undermined the hallmark of the republic - the peaceful transition of power. At least five people died, including one Capitol Police officer.

The FBI bulletin unequivocally stated that Officer Brian Sicknick "died from injuries sustained during the US Capitol breach."

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The Associated Press and ABC News contributed to this report.