Nobody bothered to put a drone in the air to keep a watch on nearby roofs.
For some reason, I keep thinking of the song “Abraham, Martin and John” by Dion. No idea why. who would equate? Maybe Andrew [Brietbart], Elon [Musk] and Don [Trump]?
Which would also give the security side the option of just flying it into the guy and disrupting the attempt.
The ONLY excuse the Secret Service is going to have for not taking a proactive shot before the shooter began is an assertion that they didn’t have a clear view of the weapon associated with the shooter before they fired (which I think will be the weakest of claims given the counter sniper AND spotter are behind peak quality optics). If they take that angle it will detail off into “it could have been a spectator” etc...
I personally can not believe they did not have the guy right in the scope from multiple seconds before his first shot.
If they had fast drone up it could get to any point in a 500 foot radius in 2 seconds plus a fraction for human reaction time. It’s a tool/option that should be in the “bag of tricks”...