Exactly. I just watched a video breaking it down, and this happened due to a series of mistakes:

1. Secret Service tells police to not climb the roof, but also says the buildings outside the perimeter are their responsibility
2. Secret Service doesn’t have a sniper looking at the only building outside the perimeter that is within range
3. Police see the suspect twice and relay the suspicious individual to the Secret Service (like an hour before the shooting)
4. Spectators see the suspect on the roof and alert police (20-30 min prior)
5. An officer climbs to the roof and backs off when the suspect aims the rifle at them (about 30s before the shooting)

There were so many fumbles here, and the shooter didn’t have any special training, that I’m surprised this hasn’t happened sooner. The Secret Service completely fumbled this one…