Secret Service personnel displayed a "troubling" lack of critical thinking as to the risk posed to Donald Trump in the lead-up to a Pennsylvania assassination attempt, according to a new report.
One man was killed in the attack in Butler this year, and two others were critically injured. All three were civilians attending the rally.
Gunman Thomas Matthew Crooks, a 20-year-old nursing aide, was shot dead by a Secret Service sniper at the scene.
An independent panel tasked with investigating the July attack has now handed down its review of the Secret Service failures that allowed the incident to occur.
The 51-page report outlined multiple communications breakdowns and accused the organisation of becoming "bureaucratic, complacent and static" even as risks and technology evolved.
"The Secret Service must be the world's leading governmental protective organisation," the report said.
"The events at Butler on July 13 demonstrate that, currently, it is not."
The review panel, which includes a former deputy attorney-general, former law enforcement officers and former homeland security personnel, was commissioned by Homeland Security Secretary Alejandro Mayorkas.
The report also provided an in-depth timeline of the communication breakdowns on the day, which allowed Crooks to launch his attack.
The ABC has previously reported on this timeline, which was also included in a House of Representatives committee interim report.
In its final report, the panel noted "no-one from the Secret Service" told the Trump detail about the suspicious person seen at the rally.
There were also not enough people protecting the American Glass Research (AGR) building Crooks climbed on top of to use as a vantage point, and a "critical" drone detection system was inoperable for hours on the day of the shooting.
"In addition to [these failures], the panel has identified a number of deeper concerns that also contributed to … enabling the assassination attempt," the report said.
"It is particularly disturbing that so many senior Secret Service agents were involved in this operation, and none of them were aware of the ambiguity at play regarding who the specific leaders with final authority were.
"The lack of such definition in practice should have been concerning to all of them."
Part of the ambiguity, according to the report, may have been "well-intentioned" by Mr Trump's security detail, attempting to integrate their own staff into the security process.
Cultural attitudes regarding resourcing from inside the Secret Service were also noted as a concern.
The review panel said it had encountered "repeated evidence" that the Secret Service viewed themselves "as operating under an informal mantra of, effectively, 'do more with less'".
"The detrimental effects of such thinking, particularly when personnel are exposed to it over sustained periods of time, can be subtle but significant," their report said.
"[The panel] has encountered repeated instances of Secret Service personnel associated with the July 13 rally failing to demonstrate … critical thinking skill.
"[A] prominent instance of this is the fact that personnel [were informed] of significant intelligence regarding a long-range threat by a foreign state actor … but failed to ensure that the AGR building was secured despite its proximity to the rally stage and the obvious high angle line of sight issues it presented."
The panel said the attack represented a "historic security failure" by the Secret Service, adding it had tried to find out the origins of the organisation's lack of critical thinking.
"Lack of critical thinking can stem from many issues and there may be a multi-causal explanation," the report said.
"Burnout, complacency, inadequate training, incompetence, resource pressure, and lack of effective leadership are all potential contributing causes.
"Regardless of the cause, it is unacceptable for Secret Service personnel to be unable, or unwilling, to think critically given the 'no fail' nature of the service's protective mission."
A lack of "ownership" by senior officials, a lack of cohesion between local, state and federal personnel, a lack of improvement, a lack of training facilities, a lack of budget and an ineffective culture were also listed as concerns.
The panel made nine specific recommendations for future events, including mandatory and explicit situation reports and sight risk mitigations and more cohesive local, state and federal leadership practices.
Some broader recommendations also called on the Secret Service to "re-focus" on its protective mission, look for "fresh leadership perspectives" and find long-term communications solutions.
"Certain individuals attract more attention and emotion — from the public, from the media, on social media and the internet, and so forth," the report said.
"Allocation of resources must be risk-based, with dynamic assessments, in practice.
"[The] threat to a presidential candidate, and the attendant loss of public confidence in the federal government if something preventable happened to a candidate, are profound.
"There were various enhanced measures put in place to protect former President Trump and others in the wake of the Butler shooting, but those measures fairly should have been expected and deployed before the tragic events that occurred there."
Former Secret Service director Kim Cheatle resigned in the aftermath of the attack amid intense scrutiny.
In the wake of her departure, former deputy director Ronald Rowe has stepped in as acting director.
Mr Rowe said in a statement following the report's release that the service was "developing a comprehensive plan" to drive "fundamental transformation" within the organisation.
"This plan focuses on increasing and retaining the agency's personnel, modernising our technology, and building a training plan that is sustainable now and into the future," he said.
"We acknowledge that July 13 did not occur because of a lack of resources, however, our enhanced protective model implemented after July 13 requires additional people, equipment, and asset capabilities.
"The men and women of the US Secret Service answer the call to protect our nation's leaders and major candidates while operating in a heightened and increasingly dynamic threat environment."
