Other occasions had Washington DC closely besieged by the Confederate Army. Of particular note - the Battle of Monocacy Junction (9 July 1864) and the Battle of Fort Stevens (11-12 July 1864), where Fort Stevens was actually one of Washington defensive forts, and where President Lincoln came under Confederate small arms fire (becoming the only sitting US president to come under enemy fire in wartime).
I'd say that's a little bit more serious than walking through the Capitol Building between velvet ropes ...
And Future Supreme Court Justice Oliver Wendell Holmes told Lincoln to “Get down, you fool!”
Lincoln immediately did so, in this stunning video:
https://www.youtube.com/watch?v=AzSq_E01qJs