You might be right, I didn't watch a second of this hearing, outside of this clip. I truly don't see the grandstanding here. She's not yelling, interrupting, asking something unrelated to the subject at hand, asking a rhetorical question, or asking an impossible to answer question.
I know that AR-14s are a bit of a hot button topic, but that is what the shooter used. It's a popular weapon in this country and it seems crazy to me that the secret service apparently doesn't do a security sweep and detail that's well inside the range of such a popular weapon. It's not like she was asking about the range of an RPG or something.