National Terrorism Advisory System Issues Bulletin
You can read the bulletin here.
The document specifically cites concerns about Domestic Violent Extremists [DVE], who it says in 2020 "targeted individuals with opposing views engaged in First Amendment-protected, non-violent protest activity. DVEs motivated by a range of issues, including anger over COVID-19 restrictions, the 2020 election results, and police use of force have plotted and on occasion carried out attacks against government facilities."
It goes on to say that some of the same groups may be "emboldened by the January 6, 2021 breach of the U.S. Capitol Building in Washington, D.C. to target elected officials and government facilities."
The bulletin asks people to be on the lookout for suspicious activity and threats of violence and to report any such threats or concerns to either the FBI or local law enforcement.
It also asks protestors to choose non-violent ways to express their grievances and encourages everyone to be aware of their surroundings at all times.