US Secret Service report details lack of communication before Trump assassination attempt in Pennsylvania

Attempt on former president's life on July 13 led to widespread criticism of agency and resignation of its director

US Republican candidate Donald Trump is led off stage by Secret Service agents following an assassination attempt in July. AFP

Latest updates: Follow our full coverage on the US election

A US Secret Service investigation has found communication gaps and a lack of diligence before the July attempted assassination of Republican presidential candidate Donald Trump at a rally in Pennsylvania.

“There was complacency on the part of" some agents “that led to a breach of security protocols”, acting Secret Service director Ronald Rowe told reporters on Friday, adding that agency employees will be held accountable.

The assassination attempt against Mr Trump on July 13 led to widespread criticism of the Secret Service and the resignation of director Kimberly Cheatle, with critics raising concerns about how the gunman was able to access a nearby rooftop with a direct line of sight to the rally stage.

One rallygoer was killed and three other people were injured, including Mr Trump, whose ear was grazed by a bullet.

A five-page document summarising the agency's key conclusions finds fault with both local and federal law enforcement, underscoring the cascading and wide-ranging failings that preceded the shooting.

The report released on Friday marks the Secret Service's most formal attempt to catalogue the errors of the day and comes amid fresh scrutiny following Sunday's arrest in Florida of a man who authorities say wanted to kill Mr Trump.

The report details a series of “communications deficiencies” before the shooting by 20-year-old Thomas Matthew Crooks, who was killed by a Secret Service counter-sniper after firing eight rounds in Mr Trump's direction from the roof of a building in Butler near where the former president was speaking.

It makes clear that the Secret Service knew even before the shooting that the rally site posed a security challenge.

Among the problems: some local police at the site were unaware of the existence of two communications centres on the grounds, meaning officers did not know that the Secret Service were not receiving their radio transmissions. Law enforcement also communicated vital information outside the Secret Service's radio frequencies.

“The failure of personnel to broadcast via radio the description of the assailant, or vital information received from local law enforcement regarding a suspicious individual on the roof of the AGR complex, to all federal personnel at the Butler site inhibited the collective awareness of all Secret Service personnel,” the report said.

The report raises more serious questions about why no law enforcement personnel were stationed on the roof the gunman climbed on to before opening fire.

The Secret Service understood in advance that the rally site, selected by Mr Trump’s staff because it accommodated the “large number of desired attendees”, was a security challenge because of lines of sight that could be exploited by a would-be attacker.

And yet, the report said, no security measures were taken on July 13 to remove those concerns and the Secret Service lacked detailed knowledge about the local law enforcement support that would even be in place.

The report's executive summary does not identify specific individuals who may be to blame nor does it indicate whether any staff members have been disciplined, though the Associated Press previously reported that at least five Secret Service agents have been placed on modified duty.