That's a good point, it probably would've turned ugly if they'd opened fire just using their sidearm. I have to imagine there's an armory somewhere within the Capitol though with "come get some" firepower in it. Hell, our local police department all have AR-15's and shotguns in their patrol cars, so I have to imagine the Capitol of the nation has something a bit heavier than that. Also, Secret Service was definitely there since they not only protect the vice president, but also those immediately in line for the presidency. You just know the Secret Service has some James Bond stuff they can deploy at a moment's notice.
Insurrection aside, I feel like the biggest question that needs to be addressed is the complete lack of security when nearly 2/3rds of our government was in one building. Any foreign power that wanted to put the hurt on the US definitely got a glimpse of just how easy it could be. If any of those insurrectionists had been armed with firearms (and maybe they were), it would've been a blood bath. Now just imagine if China or Russia had been behind it and had a bunch of trained, armed goons ready to attack the Capitol. That wouldn't have ended well.
I believe deadly force was absolutely needed here and when the National Guard rolled up it should've been all bets were off. Once the insurrectionist breached the Capitol with the intent of killing members of Congress and the Vice President, it's no longer just a riot, it's an act of terrorism and maybe even an act of war. I really hope the US never experiences an organized coup that's lead by some other than the Gravey SEALS: Meal Team Six, the Green Buffets, and the Delta-Variant Forced because we're going to be screwed.