You should avoid law enforcement work. There is no, none, zero, nada legal right to shoot anyone for the unarmed approach to a congressman, even if they broke a door or window to do so.
Arrest, yes.
There is no legal underpinning that a cop can designate a “secured zone” where he can shoot from ambush any unarmed person entering it.
And the burden falls onto the cop to demonstrate how he knew a person was armed. But even that is not enough. Say she had a pistol in a holster. There has to be a move by that person to threaten someone. You cannot even shoot them simply for being there with a gun. You can try to arrest, and that could escalate to deadly force. But by itself? No.
And that doesn’t mean congressmen down the hall hiding in an office. It means standing right there as her act indicates the congressman is going to be the target of an immediate battery from her weapon capable of inflicting death or great bodily harm.
In short, you watch too many movies, are sorely uneducated on the topic, and do not have the -slightest- concept of when and how a police officer may use deadly force.
As an example, there was a guy a year or two ago who hopped the fence, ran into the White House and through the ground floor. The President is a secret service protectee. Nobody fired a shot.
Could be. Let's talk after this plays out in court.