Second Capitol Siege Warning...Should We Be Terrified?

The FBI and Homeland Security are issuing warnings that a second "siege" of the US Capitol may be staged today, citing "chatter" among extremist groups. Does all of this sound like the scare propaganda from the dark days of the "War on Terror"? Endless warnings of "chatter" to justify further restrictions on our liberty like the so-called PATRIOT Act? Are they blowing propaganda smoke or should we be afraid?