Similar to the agency's own internal investigation and an ongoing bipartisan House probe, the interim report from the Senate Homeland Security and Governmental Affairs Committee released on Wednesday found multiple failures on almost every level ahead of the Butler, Pennsylvania shooting, including in planning, communications, security and allocation of resources.
"The consequences of those failures were dire," said Michigan senator Gary Peters, the Democratic chairman of the Homeland panel.
Investigators found there was no clear chain of command among the Secret Service and other security agencies and no plan for coverage of the building where the gunman climbed up to fire the shots.
Officials were operating on multiple, separate radio channels, leading to missed communications, and an inexperienced drone operator was stuck on a helpline after his equipment was not working correctly.
Communications among security officials were a "multi-step game of telephone", Mr Peters said.
One rallygoer was killed and two injured before the gunman was killed by a Secret Service sniper. (AP PHOTO)
The report found the Secret Service was notified about an individual on the roof of the building approximately two minutes before gunman Thomas Matthew Crooks opened fire, firing eight rounds in Mr Trump's direction just 150 yards (137m) from where the former president was speaking.
Mr Trump, the 2024 Republican presidential nominee, was struck in the ear by a bullet or a bullet fragment in the assassination attempt, one rallygoer was killed and two others were injured before the gunman was killed by a Secret Service counter-sniper.
Approximately 22 seconds before Crooks fired, the report found, a local officer sent a radio alert that there was an armed individual on the building. But that information was not relayed to key Secret Service personnel who were interviewed by Senate investigators.
The panel also interviewed a Secret Service counter-sniper who said that they saw officers with their guns drawn running toward the building where the gunman was perched, but the person said they did not think to notify anyone to get Mr Trump off the stage.
The Senate report comes just days after the Secret Service released a five-page document summarising the key conclusions of a yet-to-be finalised Secret Service report on what went wrong, and ahead of a Thursday hearing that will be held by a bipartisan House task force investigating the shooting.
The House panel is also investigating a second assassination attempt on Mr Trump earlier in September when Secret Service agents arrested a man with a rifle hiding on the golf course at Mr Trump's Florida club.
