UPDATE: Tam Pham, 48, the Houston police officer identified as part of the thousands who stormed the U.S. Capitol, has resigned.

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A Houston police officer was identified Wednesday, January 13 as part of the thousands who stormed the U.S. Capitol on January 6, according to Houston Police Chief Art Acevedo. That attack interrupted a Congressional joint session to certify Joe Biden's electoral win and left five people dead, including a U.S. Capitol police officer.

"On Sunday, I received information from an individual that one of my officers may have been in D.C. for the protest and that they may have participated in the attack on the Capitol," Acevedo said.

Acevedo said he contacted the FBI special agent in charge of the Houston office after learning about the officer's activities, which happened while they were off-duty. A joint investigation was launched into the officer, who was not immediately identified by name, but was believed to be an 18-year veteran of the department and was assigned to Westside Patrol.

The officer was relieved of duty and was served with notice of a meeting with Acevedo that was scheduled for Friday, though the chief doubted it would take place.

"There's a high probability that this individual faces federal charges," Acevedo said. "I'll be surprised if they show up Friday to my hearing."

Acevedo said once he received the tip from a citizen, he opened Facebook and found images of the officer taken while in Washington. The officer traveled alone to the Capitol, Acevedo said.

The revelation came during a planned briefing outlining additional safety measures authorities were taking ahead of the Jan. 20 inauguration. As tensions remain high nationwide after the Jan. 6 attack, cities and states are implementing similar plans.

The officer may be the first of others from the Houston area who were believed to be at the Capitol during a rally prior to the siege, though the FBI has refused to provide specifics about local citizens possible involvement in the violence and breach, citing the ongoing investigation.

"We know a lot of folks went to DC out of Houston," said Acevedo.

The January 6 incident may have been the beginning of violence planned.

An internal FBI bulletin, which was obtained by ABC News, stated that the agency had received information about a group that has called for "storming" state, local and federal government courthouses and administrative buildings in the event President Donald Trump is removed from office prior to Inauguration Day.

Sen. Majority Leader Mitch McConnell said on January 13 that if the House succeeds in impeaching President Trump, a Senate trial on whether to convict him of inciting insurrection won't likely happen until after the inauguration. It wasn't clear if there was new intelligence based on that development.

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

In addition, armed protests were planned at state capitols and the U.S. Capitol in Washington D.C..

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