…and now we know the Secret Service knew 10 minutes ahead of Trump’s speech that an armed gunman was at the venue.

That's where you're jumping to a conclusion. When he was seen with the rangefinder, he was unarmed. No one saw him with a gun until he was on the roof.

And that's the problem. A guy with a gun - even though legal at some distance away from the event - should draw very close attention. Why didn't the local cops see him wandering around with a gun? Why didn't the local cops see him climb on the roof?

Seems to me that the local cops are the ones with the major screw ups here. The Secret Service's main failure was trusting incompetent local officers. That's still a Secret Service failure, mind you. Perhaps they should have vetted the local police departments a bit better before trusting them to do such basic policing as keeping a building secure.

Let's get back the bigger picture. How do we know all this stuff? It's because an investigation is happening, that's how. And that's all I've been advocating for - let the investigation show what happened instead of making wild accusations unsupported by facts. I've never - NEVER - said the Secret Service or anyone else was not at fault. What I have said is that we don't know who is at fault, so it is premature to fire anyone or ask anyone to resign. Once we fully understand the failures, then we can ask for appropriate action, including firings or resignations.

--Peter