A friend of ours who was there - let's call him Dave - has provided some additional information about events of that day. He and his buddy, "Sam," arrived at the Smithsonian Metro station. I believe they listened to the president's speech near the Washington Monument, then walked along the Mall toward the Capitol.
They arrived at the reflecting pool in front of the Capitol at 2:20 p.m. They noticed six or seven identical silver and white, very clean tour buses (with the same bus co. markings) parked in the area.*
About 5 minutes later, Sam and Dave heard at least three loud "flash bangs" coming from the Independence Ave. side of the Capitol (outside, not inside, the building). Dave, a Vietnam era Army veteran, said the sounds were like "small handheld bombs."
Shortly thereafter, within a minute or so, a very large group of several dozen people appeared below the Capitol on the Independence Ave. side, and began moving with military precision, purposefully, through the crowd and pushing up the hill. The pace was "quick march" (in military jargon) and was noticeable because virtually all other people in the area were just milling around aimlessly.
Dave noticed the Trump flags, banners and signs carried by this group appeared to be brand new. Although virtually everyone who had rallied on the mall was maskless, the members of this large group of "quick marchers" were wearing bandanas and other types of face coverings.
He speculates that the group may have come from the tour buses and started marching on the signal of the flash bangs, although he admittedly did not actually see them exit the buses. He didn't see them at all until they started marching purposefully to the Capitol doors.
Around 2:40 p.m., Sam - who has contracts with some government agencies - said, "We need to get the hell out of here. I can't have my face caught on camera." So they immediately walked back to the Smithsonian stop and left DC. They were outside the whole time and never entered the Capitol itself.
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*I understand the MSM later tried to say those were there for the evacuation of Congressional members and staff in case of emergency, but that doesn't seem to be the case. As I understand it, while AOC was in her bathroom in the Cannon building, there was an announcement at that office building for people to go to the "assembly area." Considering all the tunnels and underground rooms in the entire complex, I seriously doubt the plan ever was for members to walk outside to buses, instead of sheltering in the other spaces provided for them.