Exactly!
Another incredulous thing I read in some of the early reporting on this assassination attempt was that the Secret Service ROI (Rules Of Engagement) specify that they cannot fire until the suspect has fired first! I do not believe that for a second. It sounds like another CYA announcement from their incompetent leadership.
Pointing a deadly weapon at someone (Especially when the person pointing it is someone already demonstrating suspicious behavior) is a solid threat and grounds for use of lethal force to stop the threat.
(Unless the target is Trump, of course...)
They changed the ROE for troops dealing with bombers trying to breach checkpoints and such in Iraq, I suppose they can do it for the USSS too.