I was a military guy, and a squad (9-10 people) of the unit I was in could’ve easily got past that “security” and slaughtered 90% of everyone there within 8-10 minutes.
Those people who invaded the capitol, luckily, were utter incompetents and losers.
Most people have just no idea how devastating and effective a fully-equipped and well-trained infantry squad from a decent unit can be.
So let’s talk about infantry squads and how they work in US doctrine. Typically, they’ll be composed of two fire teams and a squad leader. The fire teams are organized such that one can provide a base of fire (suppressive fire) while the other team can conduct movement.
Each fire team will be equipped with two M-4 carbines, an M249, and an M203. The squad will also have one of its members as the designated marksman who carries an M-4 (most often) with optical sights — think sniper for this role, but integrated into the squad. Also, recall, there are two fire teams per squad so there is just a huge amount of firepower available to even a light infantry squad.
These people train together, usually socialize together, and drill constantly. They are shockingly fast and organized when given a clear objective, even against severe resistance.
And the M249 SAW is just a devastating weapon. Regular police-style bulletproof vests will not stop rounds from those, and when you have two firing at once they will chew up everything in their way in very, very short order. Their rounds will pass through even very thick walls, too. The SAWs fire around 800 rounds per minute and will make utter mincemeat of anything in front of them. Combine those with the two M203s (grenade launchers) and the other weapons availble to the squad and it’d be a very short fight.
Anyway, using standard infantry tactics against such poor security and opposition as demonstrated by the capitol police, a light infantry squad would’ve been in that building within a minute or two and murdering everything in sight.
I am sure that has not gone unnoticed by some.